i have 3 xtm 24.7's. one in my savage..one in my t-maxx..and one in my xterminator buggy. in the savage compared to the s-25 that it came with the xtm 24.7 smokes it on low end power and actually makes the truck top out at a higher top speed. in the 10lb t-maxx the engine is jsut plain brutal. the engine is super easy to tune....the new ones with the big head run at about 215 degress all day making mad low end and good top end. i would say it is jsut as easy to tune and stays as well tuned as my OS .21 RG. on top of that the engines are very easy to break in..and i have yet to have one of my xtm's flame out or die on me. for 130$ brand new ( cheaper o ebay!) you will not find more power, reliability, and ease of use all in one package. trust me get one and you wont be dissapointed.
BTW i have heard the xtm 24.7 pro's hang neck and neck with a picco .26, but is much easier to tune and keep tuned.