string gauges and sound

jsut wondering how the size of the strings affect the sound. like if its bigger does this mean the sound would be more bassish.

The heavier gauge the set of strings, the fuller the sound. The lighter the thinner. These are broad generilizations but are accurate. I don't think I'd call it bassish, treblish, I'd call it full and thin.

Of course they also effect the sound in indirect ways, namely the difference in playability. For instance lighter strings ease wide bends, vibrato, legato, etc. In addition lower action can be set. Yet at the same time they are more sensitive to fret pressure and prolly won't last as long tone wise (which is already thin as mentioned) and break more.
While heavier ones yield sustain, warm tone, and that full sound. But that comes with slightly higher action or more fret buzz...and dead notes if you don't mash 'em down with strength.

After most shifts in gauges a quick set-up tweak is needed for action and maybe intonation for them to work best. Putting on some heavies tuned lower for the slackness may be what works for you. In the end, like most things, it's a preference or like an acquired taste.

I use the Light Top, Heavy Bottom strings so I get deep power chords and easy bends/playabilty on leads.

All lights here, its easier to speed-pick with lights I find.

SRV is a great example when talking about string guage. I believe he used 12 or 13's (very thick) on his strat. His tone is extremely full and sounds awesome, but the down side is that it's hard work to bend those.