If you are running on a newer SSD with Trim, it will zero out all the empty blocks of the physical disk to improve write performance correct? Pre-allocating a disk in VMware will have data written to each block. Forcing the SSD to first have to erase the block before writing to it inside the VM. Even though the VM thinks it is empty, the SSD sees data there. This would actually slow the write performance in an SSD environment as well as write to the disc unneccesarily. (finite number of writes to an SSD disk)
Another thing to consider is your free disk space. If you pre-allocate a disk, this gives your OS and other apps less free space. Space that will normally be emptied with the TRIM process. This comes into play if you do a lot of writes on your drive. The self-leveling features of an SSD will use empty blocks before ones it has to erase then write to. When you decrease this free space, you increase your odds that your OS will have to use a block that has to be erased then written to, thus effecting overall workstation performance.
For workstation, I actually run my VMs on a spinning disk instead of my SSDs. I find the performance for my purposes (testing) to not be worth the potential hit I would take on normal workstation operations.
