With your hull I'd go with the isolated one. When I did a motor swap in mine, I took the Speemaster mount out and put in an Octura, big mistake! The vibration of the motor goes right through the hull adding a lot more noise.
The pro of the rigid mount. Easier to put in and easier to drill the holes for the motor.
The isolated. The cons of the rigid but the the other things that I listed above.