61 keys Triton LE compared to S08? Don´t think you can do much of a comparison here - too many differences. 61 keys are not weighted, the S08 is 88 keyed and weighted.
To put it simply, a sequencer enables one to "record" midi signals (ie the notes you play, how hard you hit each key, the controllers you use etc) for playback. One usually records a number of tracks one at a time, each track for one instrument (eg. piano on track 1, bass on track 2, strings on track 3, drums on track 10 etc etc). During playback, you get all different instruments playing together. Sort of a "one-man band" concept. For a keyboard to do that, it first has to be multi-timbral (ie able to play multiple instruments in different tracks at the same time - most has 16). Both the Triton and the S08 are 16-part multi-timbral. The difference is that the Triton has the sequencer built into it but the S08 doesn´t (which means you will need a computer with a sequencer software - I think the latter comes free with the keyboard).
Maybe the questions to ask are: what is your budget and what do you want to use your keyboard for? Also, are you a pianist?