For recreational use there is no contest, S all the way. S is the one with more psychedelic effects, R is the one with more sedative/numbing effects.
I score my K about 20 mins north of Toronto, Canada. For $70 I'll get a gram of pure ketamine in the form of chunky crystals. Out of that I could K-hole 10 times easily insufflating it. If using IV, an amount the size of a pea would be an incredibly intense trip.
If you have any friends in the UK, get them to send you some! In the UK it's currently in the region of £20-30 ($30-45) for a gram. It's not as easy to find now as it was a few years ago but it's still reasonably popular. Worth a shot, as much as I love Ketamine I don't think I could justify paying like $70+ for a gram when that's at best 4 decent K-hole doses. Of course, if you've yet to try it, it's definitely worth the price - hell, I'd say it'd be worth paying $70 for just the one K-hole if you had to, though I wouldn't recommend that since you can of course get it a lot cheaper.