Step up from Addictive Drums2? EzDrummer2, SSD4, Superior Drummer? Which one should I try?

Depends how much work you want to put into your drum tracks. There's often a trade-off between quick 'n easy results versus total control. SSD at one end of the spectrum, Superior Drummer at the other end.

Superior Drummer 2 is still on top IMO. I just don't like that I can't resize it on screen (it is too small for my eyes). However, the control you can achieve through mic bleed and custom kit pieces is awesome. I also like how you can export your mixed, bussed, or single tracks with or w/o bleed as wave files.
They have not released a major update in years. Lot's of us are anxiously waiting for SD3.
 

BFD 3 is the best IMHO, but also the most complex. I must admit to using Superior Drummer most as I know my way around it so well and have my templates set up.

I have never warmed to Addictive Drums, but in fairness I have ever gone much further than auditioning the kits.

Steven Slate sounds great right out of the box but I dislike the interface.

SD2 is what I use, but I use EZD2 for quick and easy, because it sounds great.  SD expansion packs are a little pricey for me, even at that $75 half price point, so I only have a couple...and more EZD expansions that work in SD too.  I like AD because it is "different", but rarely it ends up as the final drum track.  New sounds are always fun to hear.

I should add that SD2 is the best for me when I am looking for the best quality and customization. However, AD2 is my everyday go to for writing. It's sounds are great for what I need most of the time. 
When I think I need something better, I will bring in SD2.

It seems I'm against the grain a bit here: bought/tried them all and use Addictive Drums2 all the time. They sound the most realistic to me. I occasionally use EZD's Reggae and percussions kits but not their others.
It depends on personal preferences and genres I guess, so trying demos is the best route.

Skyline_UK
It seems I'm against the grain a bit here: bought/tried them all and use Addictive Drums2 all the time. They sound the most realistic to me. I occasionally use EZD's Reggae and percussions kits but not their others.
It depends on personal preferences and genres I guess, so trying demos is the best route.

Same here...   Every one of my projects uses AD2 for acoustic drums.  For electronic/other percussion I like to use or layer Battery 4. 
 

Mesh
Yes........Demo them all & buy them all.

AS a graduate of the FSOSA, you would be expected to say that. And, of course, you are right. According to the rumor I stared with myself, when Superior Drummer3 gets here with the EZD2 features that will be the biznes. I am in saving up for it mode, though there has been no word about it. It will have been 2 years in March since EZD2 was announced and 2 years in May since release. They seem to have a big deal in May and November Metal Month. Last May was all the wonderful Muscle Shoals related stuff. I am hoping for SD3 this May.

EZD2 (and a lot of EZX expansions) does it for me.  I actually own Superior Drummer2 (as well as AD) but I like the relative simplicity of EZD2, and since the version 2 upgrade, it has all the basic tweakability I need. 
 
You can start with EZD2 and some expansions, and see if that suits you.  If you want more tweakability, you can upgrade to SD2.  The beauty is, it'll play all of your EZD expansions just fine.

I think it's worth mentioning that EZDrummer2 (AKA 'Inferior Drummer' by me) does not allow remapping of the MIDI notes assigned to kit pieces.  I believe that this is the only drum sample player in the known universe which does not offer this functionality (Toontrack indicates that this is only available in Superior Drummer, of the products they offer).
 
I've also noticed some unusual behaviour in EZD2, for example, bringing 3rd-party MIDI files (from oddgroooves in my case) into the song-creator pane can sometimes cause them to play at double-time, depending upon the order in which MIDI files are dragged in (i.e. sometimes they play in correct time, sometimes in double time).  As the MIDI files themselves are not changing, this points to a BUG in the EZD2 software.
 
If I'd known beforehand about the inability to re-map kit pieces (more fool me for not doing my research properly), I would have not touched it.  However, I've almost completed writing a TCL script which will do bulk MIDI file processing, recursively across a folder hierarchy, transposing any arbitrary set of notes to new values, writing the modified MIDI files back out to an identical hierarchy in a user-defined location.  This may perhaps be of some use other than working around the limitations of EZD2.  Once I finish it off and have thoroughly tested it, I'll give folks here the heads-up.

My favorite Drum Kit sound I've gotten is actually from a program called Drum Core.  
 
Drum Core 3 only works in 32 bit though, and it seems Drum Core 4 is still in beta testing for some of the versions.
 
With the right kit and some manipulation, I seem to prefer AD over the Toontrack offerings in general.  
 
I'm not sure any of them offer something really better for the editing side of the workflow.  I imagine you will still edit the tracks in the midi view just the same, but I could be wrong.  

NeoSoul
My favorite Drum Kit sound I've gotten is actually from a program called Drum Core.  
 

It use to be my go to. I had problems using it in the 64 bit environment, but something happend (JBridge update is my guess) and I found it was working again. I will still call it up occasionaly for some of the more unusual kits, particularly for the Luis Conte precussion. Some of the MIDI is very good, I like the Alan White stuff but its in a propriatory format so can only be auditioned in Kitcore / Drumcore. It can be draged into a DAW MIDI track for use in another program if required.
 
BUT - when Sonoma Wireworks started takeing pre-orders TWO YEARS ago I signed up for Drumcore 4 lite as a 64 bit player for my existing content and a bit of new content. So far all I have had is a rather nice 40's kit as a sweetner, there is still no sign of a comercial release of Drumcore 4, though there have been some Mac beta versions releasd.
 

AD2 is easy to use and sounds great but BFD3 takes things to the next level.  Using BFD3 with Evil Drums has me in virtual drum heaven :)  Really natural sounding drums and all the tweaking you can imagine - but you don't necessarily have to tweak anything and they sound great.  I actually love the control over the drum sounds that BFD3 gives you - bleed, resonance, etc. but straight "out of the box" they sound better to me than AD2.

BFD3 for me every time but I'm biased
 
There are demos of most of them (apart from super drummer 2) so my advice would be to try them all.
I see the EZdrummer demo only lasts 10 days so don't be like me and download it and then hardly use it.
 
All demos will have major limitations compared to the full versions but you should get a good idea of how they sound and how intuitive they are for you.
 
People say that BFD3 is the most complex but I don't think that means it's harder to use, but the fact is it does everything the others do in pretty much the same way so if you just want to load some presets, play some grooves and not spend too much time tweaking, guess what? BFD3 can do that too
 
So to some extent it's how you use it. That said if that's all you want to do with it it's a bit like having a top of the range Ferrari and just driving to the shops once a week.
 
Steve