g'day farrari,
sorry if i confused you mate, but as i understand it you do need the M1 visa for your type rating, as i needed it for IR and CPL over there which i dont see why the immigration department would look at either case any differantly. The reason why i bought the B1/B2 visa up is because you can change the status whilst inside the USA. The first time i went to the US i went on the visa waiver program and when i discovered that it was cheaper to do my IR over there on better equipment and convert it back when i got back to oz on a B58 baron i found out i couldn't change status without leaving the country so i had to go to Vancouver in Canada to APPLY for the visa (lucky i got it and lucky i was in Seattle, only 2 hours drive away). If you're unsure about training over there you can enter the country under the B1/B2 visa and change your status inside the USA to the M1 visa, you can't change your status on the visa waiver program.
PM me if you have any issues mate
V