What do you want? Do you want pvp, or do you want stats to brag about?
The pure is coming along well, and doesn't need a ton of work till its 99'd out in the stats that matter; if you want to pvp play on your pure.
The main; seeing as it only has 1 99, but most of its other stats are pretty high, you could level though and quest/slay/ect on him.
It all really depends on what you like doing in Runescape, Pking, or leveling/questing/ect.