I'd never buy a modular power supply. I'll stick with uninterupted PSU's. I've yet to see a review or benchmark of a modular PSU that holds a stable 12v rail. Everything i've seen is around 11.84+
This is because the resistance that is created by the modular plugs. "Interupted".
Also, the whole idea behind modular plugs is better airflow and removal of any wires you aren't using.
The problem I see with that is 99.9% of people that are going to go for a modular PSU will most likely going to be using all of the outputs. Also, it's not too difficult to put wire sleeving on wires if you are concerned with airflow.
I guess if you are building a low to mid end PC and you're not looking for performance or overclocking and are just concerned with the "Bling, Bling" factor, they're fine.
High-end / performance / overclocking - stick with uninterupted.