I don't really hear much of a resemblance at all aside from that Freyette and Fortin both make amps with tons of character.
The Freyette stuff is more direct and less rich overall- they sound awesome, yet don't have as much substance around the notes- perhaps they are a bit less dimensional, but very tight and nimble.
The Fortin line is more rich harmonically and also more hi-fi. There is not as much of a focus in any particular region of the response curve, but they are very well balanced with strong textural overtones. They are leaner in the sub bass department than the Freyettes and have more snarl.