It's been a while since I went through the requirements and privileges contained in EU-FCL, but if I remember correctly for a standalone IRI the requirement is 800 hours IFR and 400 in aeroplane, whereas for a FI holding it is only 200 hours. The privileges are the same and to teach both need to be a CRI(ME) or ME added to their FI rating. And the 30 (expensive) hours PIC on MEP airplanes of course for both of them. So the privileges are actually the same at the end?
I am not looking at a full-time FI career at the moment and the CRI (SE and ME) seems to be a very "powerful" rating anyway.