If you plan to race at all, you need to find out what classes your local track supports or allows to race. That may prove to be a limiting factor on your decision. If they allow MTs of either caliber (.15 or .21 or 1/10 vs 1/8) or however they class up their races, then you should be good to go. BUT if they allow one or the other, then you may have to decide based on that.
If racing isn't that important, then you are back to ground zero with respect to which truck to get.
I have a T-Maxx and a Savage. Both are excellent trucks. Both have strengths in certain areas. So far they have nothing that I would really call a weakness.
Both have great aftermarket support in the parts/hop-ups category. T-Maxx is established and Savage is getting there rapidly.
Both have excellent customer service, but my own personal dealings with TRAXXAS have left me not desiring any further contact with them.
The 2.5 is a strong engine and the T-Maxx is a great truck. You will find that the stock shocks are kind of weak. You will also find that it is a pretty fast truck. There will be a number of mods and hop-ups that people recommend right out of the box, but the stock T-Maxx is still a strong truck.
The .21 in the Savage is not bad as far as .21s go, but that is usually the first thing that Savage owners look to upgrade. The next issue would be the weak stock shocks, and then the old CVDs that come stock. The old style CVDs have a design flaw that makes them prone to shearing near the dog bone.
Take both trucks out of the box, bone stock, and I say that you have a fairly even match. The Savage is a better built truck for strength and size. The T-Maxx has an established design that makes it tough also.
For the long term cost, I will say the Savage is the best buy. Both trucks cost about the same, but the Savage is stronger and will not break as quickly as the T-Maxx. In the long run, you will spend more money on hop-ups and repairs to the T-Maxx.
Now for the newbie in you. You have to do a couple of things.
First find a good forum. You've done that here (btw try the search function...this question has been asked and answered more times than I can count in the recent past).
Second realize that this hobby is about fun and breaking things. Your RC will break and you will have to get your hands dirty to fix it. Running, breaking, repairing, running is the cycle of the hobby and is all a part of the frustration and fun of RC.
Third, don't be afraid to take your truck out there and test its limits. You will find that the only way you learn and get better in this hobby is by trying new things out, breaking things, and then fixing them so you can go out and break them again tomorrow.
Finally, above all else...
HAVE FUN!
BTW welcome to RCNT.