The titanium/coated strings have a reinforcing wrap of titanium wire at the ball end of all the strings. They also have an enamel coating to resist wear and oxidation. Longer string life and reduced string slippage.
The Reinforced (RPS) strings have an extra wire winding at the ball end of the unwound strings. Again for reduced string slippage.
I think the nickel wound's are nickel wire on the wound strings. You can also get stainless steel wound strings.
As far as which one you should use, it's personal preference. If the nickel wound strings work well for you, then stick with them. if you notice that your unwound strings are breaking easily, or that they have some tuning instability, then the RPS strings might be the answer. If you want to have more use out of your strings, longer life, and better tuning stability on all strings, then the Titanium Coated strings are the answer.
I use the RPS strings right now, but I'm getting ready to change to the Titanium coated.
Also, this thread may be better off in the EB Strings section of the forum.
Personal preference yes. I used regular nickel wound Super Slinkys 2223 for decades and I like new titanium reinforced Super Slinkys 3123 better. Great feel, tone, and longevity.
If only there was a string section on this board!!!
Anyway the new coated ones are amazing, I haven't asked but I hope the old ones are still around, the pink packet and smell of a pack of slinkys are an essential part of my childhood and I'd hate to see them go...
Yeah, I tried the new titanium coated ones on my JP and I must say I am impressed. But I think I'll be sticking with the RPS Slinkys because they're about half the price, and I have a whole box of them sitting at home .
I've been using the coated slinkys for a good while now, and to be honest, I couldn't be more satisfied! The first two sets I put on my 20th had a lemon B string. The coating would strip really quick in the most frequently "played" spots on the string, leaving it really black and really rough and uncomfortable. At first I was sort of dissapointed, cause I had gotten the impression that this applied to all of the strings, and simply settled with the idea that even coated strings couldn't resist my highly concentrated acidic build up. But when I examined them closer, I noticed that this really was only one of the strings. The G and E were both completely "fresh". So I replaced it with a new one from a set further back in the box and it now stands up quite perfectly to the rest. No corrosion at all, and the strings are as smooth and shiny as they were right out of the box. When my old RPSs would corrode completely within just a few days, these have been on my guitar for three weeks now and they still feel brand new! It's really a godsend, not to mention that they sound equally well as the uncoated ones.
I'm liking the titanium ones a lot... Seem to be a little stickier, and "softer" to bend... I have no clue why... Out of the pack they seem to be more supple than the stainless steel RPS.