Beware the trip toward "Scale" with your 3 rail. It can be a slippery slope that often plays out like this:
* Likes traditional trains and have a ton of fun with them. The center rail accepted as part of the "look". In fact, it's like a safety net: When the center rail is there, one accepts they are "playing" with trains and it doesn't matter that the traditional pieces aren't "precise replicas".
* Begins to desire a more "scale" look... and purchase a "scale" engine. Sitting next to the traditional engines it looks bigger, more impressive and "real".
* Starts gravitating toward an overall more "scale" look and eventually enough stuff is on the layout to start moving the traditional aside.
* The quest for "realism" begins and migrates into the scenery, structures, et al. Might even begin to embrace the contradictory philosophy of "3RS" with the doctrine of fixed pilots, replacing the "lobster claw*" couplers with Kadee couplers, getting rid of "pizza cutter*" wheel flanges, etc. (* = Their terms not mine.)
* Somewhere about this time that pesky center rail begins to be a real eyesore to your "scale" efforts and some frustration begins.
* Pursue such an approach long enough and one can start getting very dissatisfied with the center rail... and thoughts of going to a form of two-rail begins to be entertained. Once at this point, some have jumped ship and model in a 2 rail medium.
You can read the progression for yourself by browsing historical postings in both the 3RS and O 2 rail forums.
Frankly, been there, done that, myself... only I went to S scale.
IF I had stayed with "Traditional" 3-rail... I might still be having fun today with toy trains and a much less stringent set of "givens" for having "fun" with model trains.
Whatever you decide I wish you the best of luck and the best of fun!
Andre