Sarissae tended to be in the 5-6 meter range (15-18 Imperial feet, approx.; even longer ones were tried by the Diadochi by what I've read, but weren't worth the hassle). True pikes, in other words, and rather useless outside ordered formation. The spears used by the hoplites were of the pretty standard international pattern of long one-handed fighting spears, in the 2-3 meter range, and obviously way more manageable.

There's apparently a fair bit of debate about when, in what form, how effectively and/or if at all the "light hoplite" concept was used; but I've read the Spartans and following their example many others discarded virtually all body armour to be better able to chase down annoying peltasts and generally improve formation mobility (as a plus decidedly more men could afford to fight as hoplites when they didn't have to possess the fairly expensive body armour). The "Iphicratean" hoplite reform apparently went along the same lines, but replaced the spear with a fair bit longer one to make up for the lightened harness.

'Course, that's a bit controversial issue too.

Entirely aside from whether hoplites in lightened gear could actually catch peltasts, there's the issue that in many situations they quite possibly simply could not afford to break ranks in pursuit as that'd have left them sitting ducks to enemy heavy infantry... any enemy cavalry present would also most likely have been only too happy to pick on the now rather more vulnerable spearmen, too.