Bottom line up front: fine powder charge adjustments can make a big difference, so go get some loose powder/a volumetric powder measure and start trying 3-shot groups @ 50 yards. Start at 100 gr. and increase in 5-grain increments of power at a time until you get the best group that your gun will shoot. Then zero the gun for that charge. Odds are good that you'll never go back to the pellets once you try some more discrete powder charges.
In the majority of cases, I have found loose powder will outshoot pellets, purely due to the ability to fine tune it. With pellets, you may just get lucky and have 2 or 3 pellets shoot well from your gun, but it's certainly not guaranteed. If you're only getting 4" - 6" groups @ 200 yards right now, it's far more likely that an "in-between" load of, say, 115 gr. of loose powder will shoot best from your gun, hence why loose powder has the potential to make a given weapon shoot a lot more accurately.
For example, I use Blackhorn 209 loose powder in my T/C Omega. The difference between 100 gr. of powder and trying to up it to 110 gr. with the bullet I use is the difference between one ragged hole at 50 yards and a 2" group at the same distance. Push it up to 120 gr. and it cycles back to shooting one ragged hole. It goes without saying that those seemingly small changes in powder charge can have a very notable impact on accuracy, regardless of which powder you chose.
Last edited by Six-Gun; 02-17-2017 at 12:08 PM.