I use what the car has in real life. I mean it would be weird to use a h-pattern in a modern GT car and it would also be weird using the sequential shifter or paddles in a car from the 70s.
On modern cars I use a mix between paddles and sequential stick. I upshift with either the right paddle or the sequential stick and downshift with onlt the seq stick, the left paddle is used as a handbrake (I have the DFGT). In GT cars I use the paddle+stick, in rally I would use the stick for both up and downshifts, because the DFGT has small, wheel mounted paddles, it's sometimes difficult to find them, when you need to shift mid turn.
On the other hand H-shifter is more interesting to drive and it's even more satisfying since I made the shifter myself.And there's an added bonus of realism when you lose a gear in pratice and have to "rebuld your gearbox" (resolder the switch) just befor the race. I've had that happen a few times
But I'm improving it and it's been working better lately