200g 75g, large tank, large system... definitely the new Apex. Like in any smart upgrade plan, phase in the new system. Don't jump from what you are using now to the new system abruptly. Do it incrementally.
I have read every "problem" thread and post on R2R forum and the Neptune Systems community forum for both the old and the new Apex controllers. Sure there are some lulu's. But in every instance Neptune Systems has stepped up and knocked the cover off the ball in terms of standing behind their products and fixing problems.
I have used Neptune Systems' controllers for many years.
I will be upgrading my system soon to the new version. When I do, it will be a smooth transition. It will be done a bit at a time, not all at once.