is there a difference in running .35 over .30 wire? stronger welds? thicker metals?
as small as the difference is in these two sizes, shouldnt i be able to swap to the bigger wire with only a tip change?

Higher deposition rate, needs a bit more power. If your liner is .035 capable just a tip change and possibly drive rolls.

so will it benefit me to swap to the thicker wire?
if it needs more power, will my welds suffer because it is looking for more power?
or if it uses more power, does that mean that i can weld thicker metals easier?

Welds will suffer if you do not have enough power, ie: cold welds , not enough penetration. With enough power you will be able to weld thicker materials with fewer passes.

i have a hobart 120, flux core, 110...

Dont think you are going to be able to run .035 sucessfully with that machine, prob. need to be looking at lincoln 180 or something equivilant.

Dont think you are going to be able to run .035 sucessfully with that machine, prob. need to be looking at lincoln 180 or something equivilant.

Agreed.

The thinner the wire, the more controll you will have. I use .030 for general stuff, but for sheet metal I use .024 (I use solid core = gas tank) however I I were to weld 1/4 inch or more plate steel, I would switch to .035, for better penteration, and higher quality weld.

I have a Hobart Handler 187 (220v welder)

Oh and always match your tips and wire DIA.

I ran a Lincoln weld pak something or other 110v with .035 flux. Works like a charm on say 14ga up to 3/16. Plenty of power since flux burn so much hotter. anything under 14 and its very hard not to burn through.
Every 110v flux core machine that i've seen comes with .035 tips and rollers right out of the box.
I seem to remember .030 was hard to find too. That was a while ago.

I run a 140 MIG Lincoln 110 with .35 and it welds fine welding 10 gauge but my 180 Lincoln MIG 220 seems to do better.

.035 flux core has a lower deposition rate than .035 solid wire such as L-56. The advantage of running flux core is not having to use a shielding gas in most cases, you do give up weld deposition rate though. Running a solid wire with a shielding gas will net you a cleaner weld with a higher deposition rate.

FCAW flux cored arc welding will provide a deeper penetration than GMAW gas metal arc welding, but have lower deposition rates. Yes a higher amperage machine is required for thicker wire.