I've tried a number of bareback pads! At first, I had the Best Friend English bareback pad (
English Bareback Pad). I wasn't a huge fan... it slipped a lot and didn't stay in the middle. I then got the Comfort Plus bareback pad (
Comfort Plus Bareback Pad). This is a great pad! It's contoured and fit my swaybacked horse very well. It's actually a royal blue, not the blue-ish purple it looks in the picture. It also has D-rings, which is great because you can use a breastplate with it. I upgraded to the Comfort Plus pad with Thinline (
Comfort Plus Bareback Pad with ThinLine) because I liked the extra shock absorbing padding for my old mare. I've also ridden in Diamond Wool suede bareback pads. They are nice once they're broken in, but stiff before that. I also dislike the girthing system.
My horse has a swayback, so I love the contoured pads for her. I also like the pads with the D-rings because I use a breastcollar on trails. One thing to definitely avoid is a bareback pad with stirrups. Because there's no tree, it's common for the pad to slide side to side with stirrups, increasing the likelihood of your foot getting stuck.
Good luck finding a bareback pad that works for you!