Bass String Recommendations?

You've played upright in the past, and you'll be playing church music with the ESP, so I'd suggest flatwound strings (think, the James Jamerson sound). A plus is that you'll never have to replace them.
 
I have Pyramid Gold flats (40-105) on my Fender J bass and love them. Very pricey, though.
 
http://www.stringsandbeyond.com/pyr-bass-long.html
 
You might want to check out these as an example (your ESP has a 34 inch scale):
 
https://www.ernieball.com/flatwound
 
 

mettelus
+1 to the flat-wound. I just put round-wounds on a bass that hadn't been changed in 15 years, and the "zing" of the round-wounds is pretty prominent (mine has active pickups so makes this issue worse). In hindsight I should have gone with flat-wounds (and actually someone brought that up but I had already changed them out before I saw that advice).

Some of the hard rock and metal bass players change their roundwounds before every show. The "zing" as you call it helps the bass stand out in the live mix.
 
Problem is, the "zing" dulls after some playing. Roundwounds are cheaper, but then you're replacing them every so many hours of playing time. Good flatwounds just get better with age.

 
 
ghs have a set called 'pressure wounds'. Which are like a flattened round wound, which are a ligher brighter.
 
I have ghs flats on my Jazz Bass, and am really happy with them.
 
I have ghs tapewound on my acoustic, which are fantastic for that, nice mellow sound with less fret noise. They felt like rubber bands for a few hours, then the bed in a feel lovely.
 
Check out Scott's comaparison of flat, round and tape
https://youtu.be/ifqrU1Afd0E?t=394

Lot's of great options to choose from. All have their own pros and cons. Since I started using D'Addario strings for my 5-string bass, I'd get kudos from sound guys and fellow musicians at every gig, admitting it's the best tone they've heard in quite a while, and I'm not the best bass player around. 

I use GHS "Brite Flats", which used to be called "Ground Wounds".  
I have an old Ibanez Blazer 4 string bass (P bass copy and maybe even one of the models in the copy law suit) and with a Sans Amp (bass model) I can get nearly an acoustic bass sound out it.
 
I've used this at Cowboy Church

For a good, relatively inexpensive flat/tapewound with a good depth and thud to it I think Rotosound Jazz bass 77 take some beating, especially for Precision type basses with a humbucker (the Fender split P Bass pickup is humbucking). The Rotosound nylon tape wrap make a pretty good upright bass kind of sound that works well for some jazz and blues.

As for how often bass strings need changing, somewhere on Carol Kaye's website it says she never changed a set of strings during her decades of peak demand as a session player. Apparently, back when she was playing sessions almost every day, she'd trade a bass in every two years rather than lose work waiting for a refret to be done so the strings never had time to wear out.

Flats/tapes do keep their tone and stability much longer than roundwounds though, so it really depends on the strings themselves.

Roundwound have more treble content and twang and can help fill out a small band and make the percussive slap and pop styles work, but they lose tone over a few months or even less. Stainless roundwounds are very bright. Flats sit more in the bottom of the mix so are less likely to conflict with instruments in the mid frequencies and usually last until the frets start wearing grooves in them.

It might be good idea to get an inexpensive set of each style, try them and see what works best in a band context.

As for makes, I like Rotosound for bass (but not guitar). I suggest avoiding Washburn roundwound, they're very rough and feel like playing on a sharp, coarse wood rasp.

TheMaartian
Scott (Scott's Bass Lessons) just released this video 3 days ago. Perfect timing. Shows a good hack when installing round-wounds.
 

http://forum.cakewalk.com/FindPost/3597556

Wow, great info & links y'all - thank you!  I'm not even sure they need changed so I'll wait till my regular bassist gets back from school for the summer.  I'll send him a link to this thread and see if he wants to demo some of these suggestions.

In the early 70's I worked at a Nashville music store (I was the amp tech) and helped out in sales at times.  Rotosound's were the biggest seller to road pickers (and Ampeg B15N amps were also popular).

The bass strings that I use don't seem to be available anymore, i.e. Rotosound Superwound 606. Apparently the current equivalent no longer offers a choice of gauges. Fortunately I still have a few of the old sets left.
 
The unique feature of this type of string is the that the wound section doesn't cover the entire length of the string. Like a piano string, the windings don't start until after the bridge, so that part of the short plain section rests on the bridge saddle.