From my experiences caring for about two dozen individual cresteds and one gargoyle, I'd say they're pretty equal when it comes to handling.
It's not a great sample size for the gargs, but I've had the same experience with ones I've handled at shows.
I HAVE been bitten once by a garg at a show. I was being taught how to loupe-sex rhacs, and the gecko obviously didn't like being turned upside down and restrained. They don't bite hard enough to hurt really, but that is the only thing I can think of that might lead someone to believe that a garg handles differently than a crested gecko.
Get whichever one you think is prettier IMO.
Also, if you can, handle your gecko before you buy it. I had one super-hyper gecko who was UNHANDLEABLE to the extreme (because he tries to RUN away faster than an anole), but he was like that from the day I got him.