I went for the head and 2x10 route. Yeah it's exactly what an R500C would be, and I paid more money for it, and it's 8lbs heavier. It's also far louder then what I need, and I like it so much I'd be surprised if I ever replaced the head outside of it dieing. I'm still happy I went for the head and the 500 watt one at that.
For me it's a matter of flexibility. If I want to say use a GK 112 cab, I can. If I want to go super light and use an SVT210AV, I can. If I get a gig where there's a cab there that I can use I only need to bring a 5lb head. Or maybe I find a great deal on a tube amp head, I can use that with my 2x10 cab. I also get to leave my 39lb cab at the drummers, and bring my 5lb head home each week. I almost always play through headphones anyway at home.
As for never needing 500 watts there's nothing wrong with having the extra power there. What does it matter if your master volume is at 10 o'clock instead of 1?
There's nothing wrong with going either route though, the combo does have it's advantages like lighter weight and it costs less because of the trade then picking up a 115/112 cab.