Either way will work. If you have the capability to learn and understand the tuner it is definitely the way to go. If you are the sort that doesn't work on the bike much, get the flash and forget it.
It's a no brainer to initially upload the stage 1 flash from the tuner software, so even if you use it no further as far as programming the bike more then half of it's cost is already coverd by what you save and you end up with a very valuable diagnostic tool.
You stated before that the tuner isn't that difficult to install. Are the instructions complete or is dealer intervention required? Do you have to have a computer by the bike to do the flash and upgrade (tuner software)? I could manage that but it't not trivial. Could all this be done on a Saturday morning? As a point of reference for mechanical skill; it took me about 1.5 hours to install and set up the TSSM and about 4 hours to R/R stock exhaust with WB e-series 2-1. Both were first time and could be done faster now.
The tuner is not a installation, you just plug the puter into the bike and do your thing, nothing stays on the bike but data. You do need a laptop to fully utilize the capabilities. For just uploading stuff to the bike a regular PC next to the bike will do.
With the exception of a very few dealer wrenches the tuner will go way over their head. It can be learned and isn't that hard, but requires an element of intererst and investment of time.
You do need a certain amount of computer literacy, as for the rest the instructions are very extensive and very good.
Once you learned the thing uploading a map or editing it some should be a 10 or 15 minute thing. Couple of keystrokes.
The best puter to use with the tuner is the fastest laptop you can find, that still runs Win98 and still has a serial port.