In my experience the AE .15 is abetter engine than the HPI T15. the AE is actually very easy to tune and runs very smooth. but they are both RTR engines an d the OS 18CVR would be a very nice up gradetoboth of them. I have had several rc10gts I have had the 18cvr, 18tz engines in some of them along with the ae 12 ,ae 15, os 15cv and now I do big block conversions with them with great results! But from what you asked about I would say you can't go wrong with the os18cvr. it is a great engine with plenty of power no its not too much for the RC10GT.