Sadly I don't think there is an easy guaranteed answer to your question. The advice you quote is an excellent generalisation but you won't get much more accurate than that
FI- Possibility of some work. Hours long. Treatment by employers generally poor. Pay low. Limited scope for development. Little chance of any winter work.
IR - Higher cost, higher risk, higher possible returns.
FWIW - You may well struggle with an IR with so little hours. I know of more than two guys with more hours (400ish) that we're both good pilots and instructors (experience considered) that abandoned their IR's. They'll give it another go when they have more flying hours. The course is also far more demanding than any of the 'IR' flying you'd have completed on your CPL.
It won't help that I also know a couple of guys with 2500-3000 hours who are struggling to find VFR work aside from basic ppl tuition and trial lessons. I don't subscribe to the theory that higher hours make you a better pilot and guarantee work. Know a guy with 3000+ that is scary and guys with 500 that are more competent.
Holding an IR may help with VFR work if you have low hours as your flying is a guaranteed standard. That said to do you want to pay for an IR then fly VFR????
It's what you do with your hours, and more importantly being lucky - Right place, right time.
Not an answer I know, but perhaps a starting point might be to call a few places asking about FI vacancies (don't say you need the course, ask if they need staff). Then call the main IR providers (Bond, Bristows, SAS, and Helicopter Services) and find out what the waiting lists are like.
That might give you a starting point.........
I did CPL- FI, got disillusioned and shafted and so paid for the IR. I was lucky and have a good IR career ahead of me. But I was lucky as I qualified when demand was there. No promise it will be there when you qualify.
I'd base my decision on where I'd like to work then go for it, accepting the risks.
Thank god I don't have to make that decision again