Some additional good points were made.
I will agree it is to taste, but I found with the 20/20 (or 2:Ninety), since firmware 11.x and up it wasn't necessary to turn the amp simulator on anymore (for me at least). Obviously (and interestingly) other experiences are a mixed bag.
Also true, the comment made by "xpenno"... You do lose any power amp drive, however, So it really depends on the preset. While most of "my" presets sounded fine, there were a couple that lost their gain and need to be tweaked because of this. One again, that was my experience.
I guess the summation is, whatever works for you. =:·)