I've caught flack before for not liking cannons and instead opting to use a rifle. I've decided to put this to a rigorous test by doing a 3 minute parsed run with identical rotations but different weapons. The gear, mods, spec, and target dummy were the exact same in both runs except that in round 1 I had the mods in a rifle, and in round 2 I had them in a cannon. Here is the breakdown of major differences.
When using a rifle I had:
-1% weaker full auto average hit
-11% weaker full auto max crit (not sure on that one, could have gotten a higher one theoretically with a rifle, just didn't show up in the parse).
-0.06% STRONGER grav round (due to numerical discrepancy probably).
-14% weaker HiB max crit
-10% weaker HiB average (these two are significant, I will yield that).
-3% lower DPS overall.
-*demo round stats not included since it didn't crit during the rifle run. The 10% crit during the cannon run skewed its average.
Here is the link so you can verify these.
Overall, it really isn't that big of a deal, in PVE the burst of individual skills matters far less than the overall dps. And a loss of 3% could just as easily be due to the fact that I had an ammo hickup during my rifle run as due to the fact that cannons are supposedly better. In PVP I will concede that the loss of maximum burst is problematic, however, I can tell you that based off of personal experience, I feel as though I get targeted far less frequently while using a rifle. In the heat of a fight most people aren't going to be checking every enemies ammo cell or looking for the little class symbols.
Overall: Its perfectly viable to use a rifle for both PVP and PVE if you are willing to accept a ~3% damage nerf.
Note: This was on PTS using the provided arkanian gear.