They both have strenths and weaknesses compared to each other.
Magic System: True20's power system is flavorful and flexible, while SW's power system, in a word, stinks. SW has one the most boring and uninspiring magic systems I've ever seen. The Deadlands setting improves on it with a bunch of extra rules for different kinds of magic, but the rules in the basic book are a disappointment.
Fun Combat: They're both pretty good at this. SW's combat options are the best part of the game, and add a lot of interesting tactical thought, while SW is more like traditional d20 (minus the AoO's). The Trick and Contest of Wills actions in SW make the game IMO, while the equivalent in True20 require some investment in feats, and in the end don't come off as interestingly. True20 does have a wealth of feats that affect combat though, so a character could be designed to have lots of interesting combat options.
Mass Combat: Savage Worlds works really well when you have lots of combatants on the field. True20 NPCs have more to keep track of, and the attack rolls require calculation, so it's not as easy to do mass battles. If you borrowed the 'minion' rules from Mutants and Masterminds, where minions don't have all the standard wound levels, and are either fine or out of the fight, the two systems would become a bit closer. SW also has specific edges for PCs leading and inspiring NPCs, while true20 doesn't as much.
Character Flexibility: True20 characters can do more things than a SW character can. At each level, they gain free skill points, attack bonus, and a feat, while SW characters have to decide whether to spend each advance on combat skills, skills, or edges. There's also a lot more variety in True20 feats than SW edges, though SW is also pretty good in that regard. SW characters are generally more focused, while True20 characters are geneally more well-rounded.
GM Preparation: True20 is much easier on the GM than standard D20, but SW is even easier than True20. A GM could improvise a fully flushed out SW character on the spot, but True20 characters require some calculation.