I'd say overall I prefer Heart of the Tiger a little. It looks better, the combat is better, and it has an all star cast. Some would prefer Privateer for it's customizable ships and open world, but I still think WC3 is the better game. If you like space combat games (don't expect realistic physics though), you'll definately have fun. If you're like me you'll eventually have both.

Another thing to consider. WC3 has no expansion packs. Privateer does not come with its expansion pack. You can find and install it yourself, but it can be a bit confusing if you know nothing about editing cfg and iso files. If you just want to install and play you won't get the full Privateer experience until EA releases the Righteous Fire Expansion.

I think WC3 is simply the better game.
Privateer can be fun, but the Wing Commander feel of WC1 and WC3 (of the ones on GoG) is just that much better. I never felt much for WC2 for some odd reason.

WC3, excellent story and gameplay - also re-playable with the different endings.