I have an opinion on the matter but what do most people think the difference would be if you took a 10 year. Fixed rate, IO loan and just elected to make payments as if it were a 30 year fixed. Proviced you are not paying any additional cost for the option of doing this why wouldn’t you.
Now you need to ask yourself am I more comfortable with a guaranteed rate of return of 6% or do I feel I can invest the difference and earn a higher rate of return.
I tend to think the IO invest the difference makes sense for me. The same thing is true of life insurance, Buy term invest the diffence. Automatic investments into index mutual funds tend to eliminate teh time it would take without haeing this as an option