I personally think TT is the way to go as you have a reference every 5 laps and a personal best time to beat,where you don't with speed lap.

I've basically never played the reverse tracks unless somebody else chose them in an online tournament.[probably less than 5 times each]and I've been using TT yesterday and today to get used to the tracks, and aiming for at global top 20 time [getting better than that ATM] and it sure is helping me breeze through Arcade Perfect against the elite AI, especially if I jump straight from TT and then challenge the AI.

Pity I didn't do this when I first started the game, as I'm sure it would of made getting the elite campaign legend trophy a whole lot easier.