In Hero Wars, you:

1) Choose a hero
2) Kill with hero for more money, fight along side computer troops that "spawn" and automatically charge toward the enemy - all in a confined, elongated space
3) Upgrade hero & upgrade "spawn" and shop for accessory units as well as "waves" to help fight
4) All for the final objective of destroying the enemy's main mother building, in order to win.

The difference?

1) Map's smaller. Slow units waste less time moving around to fight--> more fun
2) All units are good ... balanced/has potential - unlike Infested Kerrigan & Tassadar that completely stinks while Zergling & Goliath rock
3) NO INGAME CHEATS. The reason why Hero Wars went into decline is that people figured out inside cheats (free $2000) by looking at replays & games became no fun
4) Faster income - game speeds up, you're constantly busy (i.e. upgrading), & game doesn't last more than 15~20 min, so you don't face the typical situation where game ends because your allies leave (b/c the game took too much time).
5) Faster gameplay means that the losing side faces less humiliation & is allowed more chance to save themselves in the next match.
6) You can't kill your own spawn to get more money. Not only do you get money buy killing spawn, you also get money on how much "territory" (i.e. location 1, 2, 3, 4, etc.) you control. By killing spawn, you lose a considerable part of your income.
7) Spawn is strong & worth upgrading. You know how some people go for immediate spawn ups & others go for all hero ups in the original hero wars? Who wins? The people with all hero ups, of course. Here, spawn is strong. This means that if the other side cheats by killing their own spawn, your spawn will overwhelm & break through enemy lines, causing the enemies to get less income. That doesn't mean that your heroes will be too weak, however. For the additional strength & capabilities, the spawn up is also very costly - thus clearing any possibility that people will go for immediate spawn up (simply impossible)
8) Waves are weak - but they can be used massively (with + $10,000, saved up -but remember you also get much more income) to end the game.
9) Different spawns, different heroes. You won't be bored.