One advantage is that it's impossible to change the system/remote's configuration by pressing buttons on the remote. If you're the only one using the remote, it's probably not going to be a problem but if kids are involved an they "want to see what this button does", it can be a problem.

Most people who want to use something other than what they sell do it because they don't want to have to learn to set up a different brand that they aren't familiar with and I completely agree with this thinking. It's not possible to know everything about every brand and model of any device or category.

If your guy really knows how to program remotes it will work flawlessly. If not, it won't. However, if he or anyone else has never programmed a Harmony, don't expect them to be eager to learn the first one on a customer's system. You won't want to pay for the time he'll need to charge during the learning curve and if he charges what you think is reasonable, he'll lose his butt on that part of the job.

RTi, URC and many other remotes are capable of macro functions that Harmony remotes can't do and it's because Harmony never intended to be CI oriented, it has always been the intention that they were to be consumer-oriented. Also, Harmony has never been good at communicating with dealers since Logitech bought the company and it wasted enough time for many that they never want to see another Harmony remote. Ask if he has experience with Harmony- that may be the reason he wants to use the RTi, but he doesn't want to dump on another brand.