I depends on what you like.
I have an Undercover and think it is the best. One person can take it on and off, no water in bed, built in light, secure, didn't cost a lot.
But, if I liked a soft cover it would not be what I wanted.
So think about if you want soft cover or hard cover.
Fiberglass covers can be painted to match your truck, or contrast. But they are harder to take on or off, and can crack.
But this is a great site to get feedback.
After all my research, I purchased the Extang Trifecta. You will find many reviews online. I highly recommend it a lot b/c its user friendly & not overpriced. (easy enough for my girlfriend to operate.) My only recommendation is to opt for the "premium" vinyl over the standard. I think it costs $10 or $20 more but the difference is noticeable.