I haven't had a 3.3 Maxx to give you a direct comparisson. If the Savage is in good condidition, it will out bash all previous model T-Maxxes. The weakest points are:
1. The stock steering servo is a bit on the weak side.
2. The turning radius is not as tight as the Maxx
3. Depending on if it's an early model 25 and hasn't been upgraded the diffs will need the 4-gear upgrade.
Of course there are plenty of things that can be done, those IMO are the most needed fixes.