Having used sliders in both City of Heroes and Aion, I much prefer sliders. The tricky part is that you have to be very careful in regards to the limits, height especially. I was annoyed to no end by the hordes of midgets that populated Aion, something that could have been fixed very easily with a minimum height requirement ('You must be at least this tall --> to ride this ride!').
The horrible part is that even if you don't look at the sliders, both of these games STILL have far more options that we do.There are at least 40 hair options in Aion, and slightly more for City of Heroes. Presets and face styles are the same - more than 10x what we see in FFXIV. This simply shouldn't be the case, considering the fact that SE has FAR more resources at their disposal than NCSoft.
I would be for allowing race/gender changes if for no other reason that reducing the number of catgirls running around the game currently. ^-^