Hey Darrell
I don't have both. Only have the .25 BP. I do have the Mini Carbine in .22 (fine gun btw) The first thing I would say is, do make the time and call Charlie, he is very easy going and will not preasure you or steer you wrong. Will probably take you the same or less time than posting here, although I think it best to do both frankly. It is an expensive investment and good research is not a bad thing.
I would agree with the above statement. The Power tunned BP will probably edge out in power (duh) and accuracy further downrange. But, you must be OK with the platform. From what I hear and know first hand they are pretty easy to work on if you have a little know how, time, and tools. I just take mine in directly to Charlie.
The .25 BP from what I understand, lends itself much better to Power Tuning due to the length of the barrel and the length of the shroud. It may be possible with the Carbine, but it is not as straight forward. Power Tuning requires adding a plennum that effectively lentgthens the air tube and you will need the space up front to be able to pull the collar beyond the moderator. The length of the barrel is also important, as it allows for the full potential of the extra air being released, otherwise it's just wasted air because the pellet would have exited the barrel and there would still be air that is pushing out, for nothing (hope this makes sense)
I too did not care for the BP and much preffer the Mini Carbine platform. But I bought one on a whim and I must admit to liking it more than I thought I would. The other thing is, this bad boy hits HARD!
Anyway, hope this helps a bit. Call Charlie.