It's really down to the individual providers.
Residential links are often shared at the pysical layer (PON), datacenter links are usually point to point. So that's a point in favor of the datacenter. Unlikely to be very significant in practice though.
The real question is what is happening further back in the network. A high quality provider will manage their network such that there is enough spare capacity that links rarely get saturated and customers can max out their connections (this generally means that their internal links should be faster than their fastest customer link, e.g. if they have gigabit customer their internal links should be 10 gigabit or better). They will set their pricing such that this is sustainable.
A provider that provides unmetered service at a bargin basement price on the other hand is more likely to leave links congested.
Size of the provider can also matter, a big provider is more likely to have direct peering links to other big providers but on the other hand they are more likely to let peering politics stand in the way of providing a high quality service to their customers.