After much bouncing around on what picks and strings i like, I've come to a stable
conclusion on the basic points...
I like the tone and the feel of really heavy picks, and I like the grip on the
Dunlop Tortex picks, so I almost always use the 1.1mm (purple) Dunlop Tortex picks.
The one exception is when I play an acoustic guitar live, I'm really prone to dropping
picks, especially if I'm standing up and singing, so I drop it down to whatever medium
picks I can find, usually a slightly lighter Dunlop Tortex.
Update: someone turned me on to these D'Andrea Pro Plec picks,
which are super-heavy (1.5mm) but play pretty easily. I'm using these about
half the time now.
I string all my electrics with 10's; there is a rough consensus that you get a fuller
tone from heavier strings, and in fact after playing with 10's for a while I find
9's a little awkward, like I'm sliding around a little too much. I've really never
experimented with different varieties of electric strings, and I pretty much stick to
the D'Addario XL's, although lately I've been trying out Ernie Ball Regular
Slinky's and I really like them (I find that the 10-gauge "Super Slinky's" feel just like 9's to
me, too light and easy to bend, but the Regular Slinky's are great).
I also occasionally use 10.5's (I know, it sounds silly that they even
make 10.5's) on my drop-D guitar; I find it's still playable and not too dark, but just helps intonation when the bottom is tuned down a little.
And I'm no expert on acoustic tone, but I have definitely learned that strings can
tremendously affect the tone of your acoustic guitar, and every guitar will sound
better or worse with some strings than others. When I had "nice" acoustics (which I
don't right now), I strung them with 13's, and experimented with various combinations
of bronze and phosphor bronze strings, depending on the guitar. On my Alvarez, I found quickly
that 13's sound awful, just too much for the guitar, so I use 12's, either
Martin SP Marquis 80/20 bronze's (if I'm playing a lot), or (if I'm not playing as much)
the same Elixir Custom Lights that shipped on this guitar, which don't sound as good
to me but last forever.
And although I've been playing bass pretty actively for a couple years, it takes so
long to wear out bass strings that I don't feel like I've really learned any reliable
likes and dislikes. Again I stick with the D'Addario XL's, for lack of exploration,
and I was pleased with the tone improvement when I went up from .045-.100 to .5-.105.
But I also definitely noticed a big change in playability, and since I'm playing less
now, the next time I re-string I'll probably go back down to .045's.