I've only used Logic so I can't compare, but I've been using it since version 5 and I must say this is the most amazing & worthwhile upgrade I can imagine.
It's always been an extremely powerful & flexible program, but now they're finally getting the ease-of-use thing down. Much much much clearer & easier to use interface than before.
I'd also recommend going for the Logic Studio package, but check out the upgrade pricing first - I'm pretty sure the upgrade is just the difference between the Express & Studio prices, so you have nothing to lose by trying Express first.
and +1 to everything Beowulf said
