In my experience (20+ years of doing this) if you're after resilience you must have local loop resilience as it's the most vulnerable part of the network. And - if you want local loop resilience, buy both legs from the same provider and tell them that that's what you want. Be clear on whether you want full separacy, some diversity or just n+1. Remember that the second leg must necessarily use a longer, inefficient route and rule of thumb is that it's going to cost 2.5 x the first leg's price.
Trying to achieve resilience in the local loop by purchasing from two suppliers never works - primarily because one will typically be reselling the other's product. You'll sit there smugly thinking you've achieved five nines on the cheap and then both legs fail at once and emails with red exclamation marks start appearing. Or not.
My final piece of advice - only buy space in datacentres with awesome connectivity. Remember Metcalfe's law.