As you move to larger engines, you will find some differences in power levels with the AX engines. They have more and it becomes noticeable as you move up in size. I had an OS 61 SF on an aircraft, and put an OS 75 AX on a newer aircraft, of somewhat similar design. The AX pulled that plane around with more authority.

Minnflyer did a review on the Goldberg Protege a while back. He used the OS .55 AX engine on this plane, and it did very well. Read the review for yourself. I bought the Protege based on that recommendation but could not get the .55 AX because they were out of stock at the LHS and he didn't expect any new engines for a month or so, but he had the .75 AX in stock. So, I bought that engine. All I can say is WOW!! Awsome engine, performance, and ease of use.

Now, I do not have a .46 AX but do have three or three of different styles, FX, SF, and so on, plus an OS 50 SX I believe, and they all run fine and have great power, AND start very easy.

It comes down to availability, I guess. Either way, you cannot go wrong.