I have a Sierra Top...I'd suggest a Robbins top. A Sierra top is approx $500 and I'd say it's worth about that much. The pattern they use isn't quite right in a number of ways that weren't immediately evident. You may notice many of the differences when doing the install, but since getting the top to go up and down properly involves a number of interconnected steps happening at once, it's difficult to tell what effect the differences you see are going to make until later. The side brackets have to be transferred over and riveted to the new top...and the new top doesn't have the holes pre marked or drilled where those brackets are to be located - I could be wrong but I don't believe that's needed on a Robbins. All of the rear mounting holes aren't pre-drilled. The distance between the two sides of the top that the strap attaches to is too small, causing the strap to be a little slack, causing the strap not to do it's job, causing the top "ears" not to pull in and causing the top to not be able to be tossed over your shoulder and go down like the factory top. The channel the strap goes through also isn't like factory....probably contributing to what I just described. The glass is probably the cheapest Chinese glass available (yes, Chinese characters printed on it)....so the rear defroster didn't work on the first top I got (the grid wasn't applied fully) and I had to go through the effort to pull that top off and put on yet another one (the owner let me keep the old top so I was able to recoup some of my personal labor costs by selling the one with the bad defroster).
Another thing that sucks is that there's no way to know whether an aftermarket top is a good choice without actually closely examining and understanding the top you have (you learn many things about the top's workings *during and after* you've removed the old top too), then comparing it to the new top....which you can't do because you're buying it online.
Keep in mind that OEM probably eliminates all these headaches.