Theres small differences.

I would definitely go with Gold, that's what I got originally and that is what I would get if they did decide to do remakes. The best version of Pokemon in my opinion...

In Silver you get to Catch Lugia fairly early on in the game, and Ho-oh fairly late. Gold is the opposite.

Then there are also the "standard" differences where there are a few wild pokemon who are exclusive to each game.

Silver, because that is the one I played.

Silver, just like I did back when I had the original game.

I'd say the main difference is the fact that on Gold you get a level 40 Ho-Oh with Sacred Fire, and later get a level 70 Lugia. On Silver you get a level 40 Lugia with Aeroblast, and later get a level 70 Ho-Oh...

Silver

Gold, since i bought Silver originally.

Silver; Lugia was the god I worshiped as a child XD

I'll be going Silver, a mate of mine will get Gold :). It's tradition for us, i always get the "blue/green" color, and he always gets the "red", which is incredibly ironic since his favourite color is a shade of blue and i hate the color blue >.<
Lol yea, i know, little sense there but we've been doing this since our primary days so eh.

EDIT: Here's a thought! Which one do you guys think will sell best? Didn't the original Gold massively outsell Silver? (i could be wrong here...)