Would like some opinions about recording guitars and bass with new strings v. slightly used v. old.

I like fresh strings properly tuned. If they are stretching during play, that is no good only because they are out of tune.

I think 'New' is a little too much. For perfection, I like 3 day old.
 
That said, My guit strings are a few years old. My bass strings are like 10 years old. If there is a problem, I melodyne it.
 
But yea, newish strings are better than oldish strings.

I always record with day old strings - or at least I start that way!

"I always record with day old strings - or at least I start that way!"
 
haha +1

Depends on the style for me....
 
Acoustics and clean electrics... I like them "broken in". Not much, just enough to take the sizzle off. "Day olds" would be a decent reference.
Country guitar... chicken pickin'? I put on a fresh set and go! I go through a lot of strings when I record this style. When everyone else is taking a break, I'm changing strings.
Overdriven guitars.... older strings work better for me. I don't care how old they are as long as the tuning is stable.
Bass: Like overdriven guitars, as long as the tuning is still stable I'm good to go. New bass strings remind me too much of 80's production.
 
Just my 2 cents...
 
 

I prefer bass strings broken in. I've flats and tapes on order, Many flat players keep the strings for ages, going for an old school sound. Jamerson never changed his strings, Carol Kaye just brought a new Bass every few years, and they came with flats back then.

I guess I'm the odd duck (I was born in Oregon) - when recording or performing, strings are on guitars for two days max. I restring half the instruments every other day. Bass, when they stop ringing and get a lightly dull sound (I prefer round wounds). I like when string rings longer. When I am not performing or recording, l leave them on for a few weeks at least. Longer on the instruments I use least. When I am done for the day with a guitar, I towel down the strings and neck and give the instrument a quick setup check. Too funny. I also stock up on strings during sales or promotions - to help save a bit.

A few other points to consider with this:
 
Acids and oils from fingers - These will degrade strings in short order. My fingers are dry to begin with, and I often wash my hands anyway prior to playing. Washing can alleviate some things (or wiping while playing), but some folks have highly acidic sweat. In a gig situation, a cloth dusted or dampened with baking soda/water would keep fingers closer to 7pH even if not dry.
 
Environmental conditions (humidity, air quality, etc.) - My guitars are rarely outside of my den, so they are not exposed to humidity shifts or most air pollutants. If in gig situations, strings would be exposed to more air issues. Not a lot to do about this one other than to wipe down strings or coat them with a protectant.
 
Pickups/guitar type (mentioned above) - The guitar I plek'd a year and a half ago still has the same strings that were on it when I got it back. I check SPAN with it every so often and it still throws all the high end, discrete harmonics it ever did (way up over 10K because the pups are rather hot). Granted, the "overly bright" sound went away in short order, but with the pups I use I do not want that anyway (I need the tone pot around 4 as it is to knock the harmonics down).
 
Quick side note with tuning - When the new nut was plek'd, I realized the approach he used was very similar to how Brian May said he had made his. The slots are actually about 1 mil wider than the string gage, so the only friction at the nut is over the saddle area. As a result, this guitar rarely requires tuning (even with an unused tremolo I have never blocked, but does have heavy springs on). For me, this has been a massive reason not to change strings, since it can simply be picked up and played instantly 99% of the time. The "Damn, that is rather nice" has outweighed any necessity for new strings.

I'm one of the people with acid sweat. I can oxidise the top three plain strings on a nickel plated set black in about two weeks playing an hour a day at home or in one gig. Less than one gig if it's sweaty. Scrupulously cleaning strings with string wipes or string cleaner (remembering to clean under the string as well as where I can see it) and wiping the fingerboard down after playing maybe doubles the life I get out of a string. When I was gigging quite a lot I'd expect to go through a set of strings a gig. On the positive side I haven't broken a string on one of my own guitars in over 30 years.

I don't seem to do anything like as much damage to round-wound bass strings but then again I don't play bass as much as guitar.

As for fresh strings being over-bright, on Teles I use Fender 150s. The pure nickel wrap means they put out less highs in the first place so there's less sizzle and a warmer, smoother tone even with brand new strings. My SG gets Gibson Brite Wires, which compensate some for the decreased treble you get with the 300KOhm volume pots Gibson have used on lots of guitars for the last few decades. The ES135 gets Fender 250s in a heavy gauge for slide playing and my bad impersonation of John Lee Hooker.

Thinking about it, what I aim for, besides not playing on rough corroded strings that won't stay in tune, is consistency. If the strings are always pretty fresh it means they're consistent and tonally predictable. I deal with any new string tuning instability by repeatedly pulling the string away from the fingerboard up and down it's length until I've got most of the stretch out of it and it's stable.