Having run both the .25LA-S and the Magnum XL .25 (hecho en China, a twin ball bearing engine), I'd be happy using either on a Ringmaster. Find the right prop (around 4" pitch), and you'll like either of them. The Magnum will probably last longer, because it is twin ball bearing and real ABC, not ABN, but neither is a huge deal. I'd say that if you can get a nice Magnum XL .25 or .28 at a good price, go for it. They have been advertised for around $50 new from Hobby People, so bear that in mind. $25?
I don't know anything about the Taiwan version, but since parts are probably not available, I'd probably pass.
The deal is that I don't like the plastic backplate RN setup on the OS, tho I did try it. Fuel ran back to the tank after choking, so starting was not great. The plastic backplates may be ok, or not, but I don't like to have problems when I'm at the field, so always change them out (also on the .40/.46LA) with aluminum ones. And a good .156" spraybar through the venturi. The stock size venturi works fine, but I drilled mine out to .272", and that also works fine.
With the Magnum, there is no CL version, so you need to get a venturi made for it. Mine has a .257" venturi bore and a .156" spraybar through it. This is on the small side...I'd suggest .265" as a happy size. The Magnum muffler works ok, and is lighter than the equivalent OS muffler, but the engine itself is heavier. Fox .35 and OS .40/.46LA mufflers bolt on, if you need nose weight. Their rear NV assy is excellent, but would probably suffer the same starting problems as the .25LA. Not a problem if you use an "electric finger".
Steve