Well, it's rather difficult to compare such a game to StarCraft. StarCraft was entirely 2D, because of that, the game can support up to 200 supply per player (unless you mind control units). WarCraft supports 90 supply no matter what due to the increase in graphics by using 3D graphics, and superior details in graphics, along with all the triggers, etc that come with each map.
mynameisishmeil is correct in how it's similar to merging D2 with StarCraft, however I personally still prefer StarCraft. Heroes make games very unbalanced in multiplayer if you're level 2 and your opponent is level 7+. StarCraft requires much more planning as you can't use just one unit to wipe out most of your enemies units.
I spent $80 to get the WC3 Collector's Edition box set with Soundtrack, DVD of all the cinematics, collector's artwork, and a 200 page booklet of WarCraft art from WC1-3. After about 3 weeks of gaming I found myself only going on WC3 to play the RPGs due to the excellent graphics and crazy triggers. However even that got tiring after awhile, and I ultimately reverted back to StarCraft. The only sure thing you can do is download the trial version of it and see if you like it. Everything you'll read are opinions based on personal tastes not necissarily similar to your own.