I had this exact same discussion with somebody who got into LBS and MIT in R3 a couple years ago. She said the below -
1. Apply R3 only if you must
go to school now, and absolutely cannot wait another year. This is based as much on chances of getting in as other things like scholarships, time-off before school, etc etc.
2. If you must apply R3, make sure you address specifically why you're applying late in the optional essay. And this reason better not be that you simply couldn't be bothered to apply earlier. Or because you got dinged everywhere else and this is last-chance motel.
3. R3 is actually not that much different from R2. If you're a strong applicant, you'll get in just the same. However, at this point, most schools are looking to round off the class composition and have filled most of their cookie-cutter profiles.
Hope this helps. But Milias, dude, we're both so getting into Ross, so don't sweat it.