some strings are pure nickel strings and the others are nickel plated steel. pure nickel will give a more vintage tone and steel is a bit brighter. i think the nickel plated steel has a better bite to them then the pure nickel strings.
Strings are probably one of the most subjective topics amongst players. I've used both and like both. The big variables will be 1) what kind of music/styles do you play? - and - (2) what kinds of guitar(s) will you be using them on?
Nickel Plated Steel (NPS) is found by most to be a better R&R to hard rock string. More crunch, bite, etc. Pure Nickel is warmer and lends itself nicely to clean tones, vintage blues and country tones. Pure Nickel also sounds good with single coils. Because it is warmer, you may find it to be a bit too subtle for some guitars....particularly mahogany body/set neck guitars.
I've used both over the years and, more recently, on my 25th Anniversary with good results. However, I settled on NPS on this and my Reflex.
Depending upon sale prices, I seriously suggest dropping the $10 for both sets and take 'em for a spin. Like I said, strings are very subjective and everyone's hands and playing approach differs.