I've used both SRAM and Shimano. I really like SRAM because it has a more compact feel, and I believe the lever throw is a lot shorter (especially with Red and Zero Loss). They've advertised it to have a 1:1 pull ratio. So however far you push the lever, that's how far the rear derailleur moves (3mm to shift)... At least I think that's what it means.

I use SRAM Rival shifters and have it to the smallest setting. Not because I have small hands, but I like how they feel. Also SRAM has a dedicated shift lever that isn't integrated with the brake lever (like Shimano). With SRAM it's a lot easier for me to shift. In the drops I can easily upshift three with a single finger. I push the lever over and towards me. You can't do this with Shimano, because you'll pull the rear brakes.