RE: loose powder or pellets
Triple Se7en is a dream to clean. Simple water, a little scrubbing, and it comes right out. You also get more shots per pound because it is 15% stronger then Pyrodex or Black Powder. There is less stink when you shoot it in my opinion. I feel is ignites excellent, even with the #11 primers in the sidelocks and the Knight Wolverine.
There are some disadvantages too. Besides the extra cost, some people experience the dreaded crud ring. I personally swab between shots and do not shoot magnum loads and crud build up has never really been a problem. I was also told it like to attract moisture but again, I have never seen this as a problem. It sure can not be as bad as the old Clean Shot.
Some rifles like it, some rifles hate the stuff. I have two sidelocks that do not seem to like it, yet they shoot excellent with Pyrodex P. My inlines seem to like Triple Se7en without doubt. Although they shoot with Pyrodex as well.
The best thing you can do is give it a try. If your shooting in lines be sure and check your breech plug after so many shots to make sure it is still moving.