Hey, I just switched Dixie over from ProZinc (8 months) to Lantus this week. Check out my spreadsheet, although keep in mind the ProZinc was an old bottle which, when combined with the low dose, would likely cause inconsistencies (but it still got her down to the greens!). I liked the ProZinc, but I ended up with the issue that a very small dose (0.25u) would drop her BG levels a lot, so I could never increase it in order to get lower preshot values. I took note of this, then made the switch to Lantus and now her BG values are very level and don't jump up anymore (fingers crossed!).
I don't know anything about your current insulin, Novolin N, but it looks like small doses were really dropping his BG levels down. I think Lantus would be a good one to try. See if it works, and you can always switch to ProZinc later if needed. I also think Lantus would be suitable because you already have experience with giving insulin and getting the whole schedule down. One of the reasons I liked ProZinc so much in the beginning was that it gave me more leeway in timing everything while I was learning the ropes. But once I got the hang of things with ProZinc, the switch to Lantus was trivial, and I think you may find the same.
Lantus is very popular here (check out how busy the Lantus forum is verses the ProZinc one), but you will get good support on either forum. My current vet recommended Lantus to patients for a decade, but has found a lot more success with ProZinc, so they switched over to it. It's really going to depend on how your cat reacts to the insulin, so you can't really go wrong with trying one or the other out for a few months and see how it goes.