To be honest, I have no idea what "modular" means. Maybe it's country specific? I'm based in Canada.
I ask the question primarily because, I get my CPL after 200 hours, and 35 of my remaining hours are "on-my-own" time. During these 35 hours, I could have fun and whip around on my own (not very cost-effective), I could go for a Multi-IFR, or I could go for Instructor's.
Instructor's rating is quite expensive, and if I can avoid it I'd like to. If you think I'll need to work as an instructor at some point, might as well get it over with now!