I have had a Savage and a Revo, and I have done tons of research on converting both trucks, and had all of the parts to convert the Revo. I got into crawlers and had $1500 in my Revo and hated for it to just sit on the shelf, so I went ahead and sold all my stuff. I have a brand new Novak HV Pro brushless system that is perfect for a Revo or Savage. It's never been out of the box, and I'm selling it for about $100 less than it costs if you buy it from a retail shop or online store. If I were you I would convert the Revo. The Revo is a lighter truck and it handles better, and when you do the brushless conversion it's going to run, handle, and race like dream. The Savage doesn't handle nearly as well and is a lot heavier. In fact, I sold my Savage just to buy a Revo for the conversion. I've talked to several people who have Savage conversions, and they all wished that they had bought a Revo to convert instead because they handle so much better.
The cheapest way to go by far is to buy the E-Revo, but since you already have the Revo it might be cheaper to convert it. If you take care of your rigs and you haven't ragged out your Revo, you could sell it and buy an E-Revo. Then the only thing that you would need to buy would be the brushless system, and you would have one hell of an electric Revo. The power and torque from these motors is unbelievable, and you're going to wonder why you ever ran nitro. I always said that I would never have electric, it seemed to boring and I was one of those guys that said "I'll never have anything but nitro, electric is for wimps." Well I was stupid and ignorant, and once I saw how much more powerful and responsive the brushless stuff was, that was all it took. I also have a 5th scale baja, and I'm strictly into 2 stroke gasoline RC's and brushless RC's with Lipo.
Feel free to post any questions that you may have, or shoot me a PM with any questions. My Revo build was going to be my most intense build yet, and it was a ground up project, from the carbon fiber chassis to the suspension to the sick custom graphics on the body, so I have done a lot of research. However, if the E-Revo would have been available then, I definitely would have bought it instead of doing the conversion, because it's so much cheaper, and it's set up better for electrics.