Avent vs medela pump?

I have been going back and forth with which pump to get...fortunately insurance will cover both so cost isn't a factor. I am panning to straight breastfeed as I can take about 6 months off work so not sure how often I would be pumping but still want the better option for when I do have to pump. I have a larger chest and not sure if one is more comfortable and effective over the other. Also I really like how avent has natural shaped nipples, not sure if that should be a factor. Which worked best for you-medela or avent?