My daughter is 2 months old. I've been exclusively pumping since week 3 and have had the chance to use many different brands (thanks to my older sister and all the extra bottles she had leftover from her babies).
I started with Dr. Brown's - they were ok for a while but then she started to choke and spit up A LOT. She was gassy for about an hour after every feeding.
Playtex - She was okay with them but again, still spat up after every feeding. Still gassy.
Born Free - Not bad. Didn't spit up as much but too many parts to wash.
Avent - LOVE them. No spit up. No gas.
I haven't tried Medela. But I'm planning to stick with Avent. Every baby is different so if you can, try every brand until you find which one works best for you. :)