just more suitable, closer rolling diametre, the 245/45 is just too much profile for a 17" for street tyres on a skyline, and yes they will look better as well.
but he's^^ right too, 235/45 is the cheapest option if u are willing to go to the 235, for the price u are able to get 235/45's at, u would be better spending the same amount on a 235/45 and getting a better tyre, as on a 245/45-40 and getting a lesser tyre.
i just wouldnt really bother with the 245, if u wanna go a bit wider, go to the 255/40.