As an owner of a TRR8, there's really no choice but to go with the TRR8 vs. the R8.
-With both rails being removable, you can realistically find a holster to fit the gun. The big, vertical Bianchi hunting rigs work, but only barely. I can't imagine anything but a custom one-off race gun chassis could hold an R8 practically.
-Don't listen to any naysayers suggesting an a steel frame is worth it. The aluminum frame is light as a steel gun of 'normal' size so recoil is perfectly reasonable even with heavy loads, but the large grip & frame size give your hands lots of room to spread that force over & enough leverage to keep the muzzle down.
-Trigger on my gun was pretty darn nice, only guns I've shot that seemed nicer are the SA on the Mateba Unica 6, and the DA on the Manurhin MR73. A vintage Colt may be nicer, but not by enough, frankly (and would be both far heavier and way too expensive/delicate to do much besides safe duty; the TRR8 can be reasonably serviced if need be)
-Quite accurate, at least far more so than my abilities can reveal. The 5" barrel is the perfect midpoint between long hunting rigs with extra sight radius and the concealable ones that are less practical to use beyond a dozen or two yards. That length also helps counteract some muzzle rise, since the aluminum frame results in a slightly more barrel-heavy balance (feels neutral to me for an N-frame, though). The gold bead front sight and post make for a very nice sight picture; the post is a little wider than you usually see, more like the ~1/8" seen on service autoloaders these days. For low light, you'd really want night sights or better yet, a red dot (or laser, as your preference dictates, since you have all the options with the rails)
-I understand the barrels are the same now, but at one time the R8 used polygonal rifling, which was cool and all, but kind of a dumb choice for a chambering like 38/357 where cast bullets are so common.
-The either shot is worth the premium and size over the L-frame 686+'s to me. Puts it in true autoloader territory for capacity with only a minor step up in size/weight (and a Scandium L-frame is getting into the handful realm anyway) but with much more headroom for firepower in each shot as well as improved reliability. I believe the guns have some feature advantages over the smaller models as well, such as the forward ejector rod support/latch, and being set up for moonclips
TCB