And here we see something pretty interesting too: How many Lands should I play?
I'd actually say 20 Lands, 8 years playing MtG has given me some experiance

Now seriously , I prefer really fast Decks when you can play 75% of all your cards during your 4th turn, and I think much place can be saved wen runnung a faster Deck, you can calculate this very easyly:
When you run 30 cards and have 20 expensive creatures, it takes you a while until they're out.
But running 20 Lands and having 30 less expensive but also expensive Creatures like Watchwolf, Jötun etc., you still get "the same amount of power", as I say.
Even in Control, I run just a maximum of 22-24 Lands, cus there actually are (or were) "cheap" Control Spells like Cryptic Command (I own 2). Paying 4 mana isn't so hard at all, but you can get nearly everything with that spell.