The crennellation can shape teh outer edges of the beam slightly and of course its sharp so theoretically you could poke or whack people with it. The real concern is if you or the people you are giving it to might worry about hurting them selves with it you know, like if it is in a pocket or something. I guess the flat bezel also makes it a tiny bit smaller. It is not a huge difference, but I personally got the flat bezel.
I have a normal rc-n3 and it is a great light and I'm sure the r4 version is that much better. The r5 dropin just came out tho so I wouldnt really know how good it is or what the beam profile looks like while there are many positive reviews on the rc-n3. On the other hand though the modes on the romisen are not very good and it isn't upgradeable. Basically, the solarforce is probably a better choice, but I can't really say for sure.