Yea I think they are fairly close, with Imperfect Cell being stronger of course.
Imperfect Cell is a huge ki power to Vegeta SSJ, though Kuririn also considered Tenshinhan and Yamcha's ki huge, so I'd not take such comment at a face value. The issue is, Vegeta grouped Cell with Kamiccolo and said he's been surpassed left and right, that is Imperfect Cell [Ginger Town] > Vegeta SSJ. But when Cell senses Vegeta on the move, he's suddenly somewhat worried and notes that he will have to hurry up. That is, Vegeta is at least relevant to Cell, so I would not have that much of a gap between them. I'm going with 1.15x, i.e, Vegeta SSJ being 87% of Imperfect Cell, which is fair enough.
Piccolo 75
Trunks SSJ 88
Goku SSJ 95
Vegeta SSJ 100
Imperfect Cell [Ginger Town] 115
Kamiccolo [Weighted] 135
Android #18 140
Android #17 150
Kamiccolo Full Power 150
Vegeta SSJ is 87% of Imperfect Cell and the latter is 85% of Kamiccolo [Weighted]... seems pretty good.
I have Vegeta SSJ ~ Future Androids, so this fits pretty well with Cell wanting far exceed them to absorb them, since they're at ~87% of Cell, that is, Cell cannot take the two at once, but is stronger than each of them.
Kamiccolo ( Full Power ) ~ Present Android #17 > Present Android #18 ~ Kamiccolo ( Weighted ) > Imperfect Cell > Future Android #17 ~ Future Android #18 ~ Vegeta SSJ >= Goku SSJ > Future Trunks SSJ > Piccolo.