Don't get too caught up in the recommendations toward one brand or another. In the past OS was definitely the standard but there are many good competitors nowadays which often make the OS equivalent look overpriced. Like others have said, you will get more bang for the buck if you get a ball-bearing supported engine so I would suggest making that your focus.

I have two Thunder Tiger .46 Pros and love them both. The .61 Pro should be every bit as good but I believe there are other .60+ size two strokes that are lighter than this particular Thunder Tiger. I have read many good reports on the Tower .75 and it weighs in about 3 oz. lighter than the TT .61 Pro (ball bearing) engine and slightly lighter than the OS .61. For the price it is probably the best bang for the buck. I suggest doing a search on this engine to find out more.

Just be sure to run it rich for a while and don't push it too hard and it should break in fine and give you many years of service if treated right.