I think I prefer the flattops, alot of options for optics that are better than the sights on the carry handle. I think the carry handle has a nice classic M-16 look but how many people actually use it as a handle. I love the visual of a flattop with great optics and gear, looks like you mean business. The carry handle seems to make the gun seem toyish!
For me I have a flattop Sabre Defence with a detachable carry handle. It sits in my gun room and the rifle is equiped with BUIS and either an EoTech or ACOG, depending on my needs.
I have never tried my handle on my AR, I think it will never be mounted because I love the current setup.
If I had two AR's, then I'd maybe think about getting the second with a carry handle just for the historical perspective!
For me, I like the modernized flattop AR's.