7th Gai's speed > Full LRA Armour Ay's speed.
For a simple, clear reason. Ay's LRA utilises the electricity to stimulate the nervous system, therefore reaching his body's limits.
But, as we know, the Hachimon are designed to 'break' the limits of the body, enabling the user to perform inhumane physical feats, like speed.
So, because the Hachimon frees the limits that LRA can't, Gai is faster than Ay with seven gates opened.
Of course, because of Ay's sheer raw speed, too few gates might not be comparable, like Lee with five gates open.