I would opine that there would be little difference in sound quality between the two and even compared to the Soundcraft. Unless you had all three in one place and did a detailed blind test you cannot really make such statements that one mixer is a lot better than the other. Mixers are a lot better today than they used to be.
 
Both are good but I see the Yamaha has got more channels, compressors built in which could be handy and effects. It seems to offer more all round. The Mackie will do the job too and will have a very transparent sound.
 
I use a Samson mixer to mix the analog sigals in my studio and I have found from experience that the effects are handy and can be very useful at times. The compressors could also be handy for taming a wild synth or something before it goes into your DAW. I think maybe look at the features and decide which one would better work for you. The sound from both of them is going to be good enough for what you are wanting to do.
 
Given what Cactus has said though the Yamaha maybe the better option. They have always been pretty consistent in their construction and reliablity.
 
Just out of interest the Samson that I use is this one and I cannot recommend it highly enough.
http://www.samsontech.com/samson/products/mixers/mdr-series/mdr1688/
It has got 16 inputs, 8 Mic Pres and 4 stereo line inputs. It seems to match all my input sources beautifully. The EQ on the Mic channels is slightly different to the line inputs too. (both EQ's very versatile) The HPF works very well. It is ultra quiet, has a very musical sound and the effects are excellent. It is solid and well built. Nice small footprint too. One of the reasons I got mine. It had to fit on top of a half rack.
 
It would be a cheaper option but you may want something slightly bigger and in that case the Yamaha would be a good fit. I got it for around $300 here in Australia. (180 pounds in your speak) The shop you refer to only seems to have the 12 channel version but you could ask them about the 16 channel model.
 
 

mike_mccue
 
I'd opine that the sound of a Soundcraft GB2R 16 is a huge step up from either of those.
 

 
best regards,
mike

Ooooo, that's pretty!  I've got a Soundcraft Spirit M12 and that one could take it's place quite well.

Looks like that model Soundcraft may be out of production like my M12.  Too bad.



 

Cactus Music
I just bought a Yamaha mg8cx which must use a lot of the same components. Your choice is just bigger. I wrote a review if you care to see what I found. I like Yamaha stuff over all as it sounds good and seems to last the longest of all the gear I ever bought. I would also check out A& H stuff. The word is that Mackie is no longer the company it was and their stuff is declining in quality as a result, so approach with caution. 
 
http://www.gearslutz.com/board/reviews/843873-yamaha-mg82cx.html

 
Not to toss a can of starter fluid on a lit BBQ, but just go tweak the faders on a Behringer and then do the same on a Mackie, or a Yamaha. Times change.

Some interesting thoughts here.
 
Keep 'em coming, I've got about a month or so to make a choice!!

Let's just say that there are occasions when, having regrets at ever letting go of an A+H Mixwizard, I find myself browsing fleabay for another...

A+H desks get a lot of love from all over the place.......

If you read my review you will see I would have bought an A&H hands down, very nice, It was the best of all the mixers I tried but was also $100 Can. more than the Yamaha,, and was  2x as big. I have "big" already with the 01V. I think A&H would be top of my list if I was  looking for a 16 channel for a band or multi tracking. But my 01V refuses to die after 25 years. Well one channel is dead but that was my fault -- a phantom power abuse issue. We just used it again tonight at Music in the Park. Yamaha Mixer, Yamaha power amp and Yamaha speakers, All 25 years old and still sounds great. ( Yorkville sub,Yorkville bass amp, Fender Princeton amp, Roland Keyboard into a Peavey K 100. ... We had a Mackie Mixer back when, only lasted about 10 years, was great stuff but certain brands seem to break and others go forever. one of them is Yamaha. At least I hope the new stuff is the same,,, The made in China thing scares me sh--less. `I miss "Made in Japan" or even Korea. And of course Mackie WAS an American made product too. Is Peavey still made in USA?? Yorkville is still made in Canada ( I think?) Soundcraft was GB? 

It's really hard to say what's what these day when it comes to gear manufacturers. There's been a lot of takeovers and consolidation, and a ton of off-shore manufacturing. A lot of brands are noww owned by corporate parents, and many of them share resources. Look at what happened to M-Audio, the first thing they did after Avid sold it to InMusic was to re-badge some Alesis interfaces. Alesis and Akai don't have the product breadth they used to. A strange story is Chinese manufacturing. Behringer got rightly beat up for quality issues years ago, so they dumped contract manufacturing and built their own plant over there. I'm not sure about Mackie, although they seem to have been in a funk. Certainly, they've let the MCU product line stagnate - no more C3 unit, not sure if the fader expansions are still available

Baby proofing a room takes four easy steps:
1) get a hammer
2) go to the room that needs baby proofing
3) get down on your hands and knees
4) crawl around (on your hands and knees) and smash everything you can reach with the hammer