The Intergrated path is the chosen route for the Oil & Gas industry. They (oil companies) demand Integrated Training or you need to have hours and experience under your belt before joining - I think the requirement is 500 Hours, which ties in with the current job advertisements. But the standard Catch 22 - Low hours, no job - And if you haven't got a job, how do you get the hours. The integrated training allows the offshore helicopter operators to get around this problem and provides the highest quality of professional full time training.
The integrated path is probably the cheapest route also, as it requires less hours than modular. It is professionally well accepted and would be a good route into any job, but you are still going to have to have realistic expectations about your first role in industry. Oil & Gas will employ direct from training with an integrated course. You may also get a Co-Pilot role in some onshore operations, safety pilot etc, but it can be difficult to build hours. Taking a role as an instructor is always a good way to gain hours and experience, but you can feel like you're still a bit out of your depth - Teaching others while you are still learning yourself!
If you have doubts about the Integrated Course, just go with the modular. It will cost you more and take longer, but you can pay as you are going along which can be an advantage if you don't have the money to pay up front - And how many of us do. I'd be surprised if your training on the integrated course wouldn't count for anything, or allow you to drop down to modular course if there was an issue. Not sure where that theory comes from. You will still have to gain hours from somewhere before gaining employment in most careers, so you might be limiting yourself, depending on your end goal. You asked about originally about becoming an instructor, so if that is your aspiration, the modular course is fine, and if you perform in your training, the whole course is like one long audition and job interview!
Good luck