Whats the difference? Is it the same but with silence? Which one is better?

Depends on the situation. The first does more damage, but the second doesn't attract enemies.

You have to take into consideration that really, neither is a particularly good weapon and only useful at low levels. The silencer is useful in theory, but in practice it's very difficult to get a one-shot sneak critical with it, which leads to alerting the enemy anyway.

Both are really only viable with the Defender Perk. After I get this perk, I use Wild Bill's Sidearm, though the damages for these two weapons grow respectably.

Not if you use the WMK mod and put one on a .44 Magnum. I can't quite take down a Super Mutant, though I come pretty damn close. Raiders drop like a rock.

I wouldn't use either. Even at low levels there are better weapons to find than a 10mm pistol. By the end of Moira's Super Duper Mart quest I've got at least a hunting rifle and assault rifle both of which put a 10mm pistol, silenced or otherwise, to shame. It doesn't matter if they can't hear the first shot, their still going to feel it and there going to attack you just the same. It's too weak to really kill anything in one shot with. Besides you'd be surprised how deaf enemies can be. In reality the sound of gunfire travels quite far but in Fallout 3 it appearantly fades to silence after about 30 or 40 yards. Enemies only really notice my gunfire if I'm shooting directly at them.