IMO it really depends on your shape/breast size. But I can tell you what I like (and I have tried quite a few over the past year). For reference I am a 36C while BFing and wear about a size 6 pant size.
My absolute favorite is Boob designs. But they are hard to find in the US and super expensive. However, they fit amazing and I love the way there nursing opening works. I found one place that carries a few of their styles for reasonable (for this brand) prices. Here's a link:
http://www.nurturedfamily.com/nursin...hing-tops.aspx
As for something more affordable, I have actually really liked Old Navy's nursing tops. They have very few styles and they are hard to find in the store, but are easy to get online. They seem to run true to size--I always wear a M in Old Navy tops and the M in the nursing tops has also fit well. They hold up to lots of washings and are my most used tops. Some of the Gaps tops I have liked too, but those are more hit or miss I find--often the nursing openings are award or weirdly placed/too visible, but when you look at them online they have reviews that are usually pretty accurate.
I also just use nursing tanks to layer under normal shirts and this works well for a lot of tops.
). Any brand suggestions? Any brands I should avoid? Web site links? TIA! 
