There are some notable differences.
The 305 uses the traditional fender scale length (nut to bridge) of 25 1/2"... the DC3 splits the difference between that and the traditional 25" PRS scale by going with a 25 1/4".
In theory, the longer scale length should give the 305 a little added "snap", but the DC3 is actually the snappier of the two because of the bolt-neck configuration at the heel. The 305's neck is a glued-in set neck.
I find the 305 to be a bit smoother sounding and the DC3 to be the more "stratty" sounding of the two.
Also, the 305 uses brass bridge saddles... the DC3 uses steel. Again, possibly a "snap" contributor.
The only one I don't understand is the Swamp Ash Special. It's also maple neck, and carved top like the 305 (the DC3 is a flat top with a pickguard) but sticks with the PRS 25" scale. I would have thought PRS would standardize their bolt on necks to all be 25 1/4.