MIA to SEF is around 50ms on a good day. MPLS providers will set their SLA around that value, so it's a pretty good bet the Internet as a whole will have some induces latency. Don't forget all the regeneration of signal and hops along that airmles route.
Ask the high frequency traders, ad providers, or other brokers how important latency is and you'll get a different story. There's a good reason people colocate at 111 8th or other downtown locations in Manhattan then across the river in Secaucus NJ. Data centers are always going to be a) close to the companies that house CPE there; b) close to others they wish to communicate with (NYSE, NASDAQ, CME) and then close to the carrier hotels (1 Wilsire, 56 Marietta, etc), and backed up by SLA driven networks, not just Network Service Provider connections.
PUE is more achievable in homogeneous DC's that Google, Facebook or Apple run. It's harder to get a PUE under 1.8 when in a heterogeneous data centers. It's hard to convey to customers that their per-kWH cost isn't just a markup on the utility power, but everything else that goes along with cooling, maintainability, and DC operations.