12v/24v charge setup question

[stelo]

I have been searching around trying to figure out an ideal charging set-up that I won't need to upgrade from. I will likely grab two feathermerchant PSUs in plug-and-play (24V47A Plug-n-Play Supply http://www.feathermerchantrc.com/) with an big charger like the 3010B or a Powerlab v6/8. I have a couple questions with regards to other peoples set-ups that I have seen:

- Why do people run both 12v and 24v set-ups with two chargers, I understand that they are charging 3s on the 12v charger, and 6s on the 24v charger, but why do they need to do this? Can't you just have one 24v setup and charge both your 3s and 6s packs off that?

- As a follow up to my previous question, instead of having two chargers running off two PSUs in series (one for 12v and one for 24v) could you just have say a 3010B and when you want it for 12v just plug it in to a 12v port, and when you want 24v just plug it into the other leads on the PSUs for 24v (assuming you have your two PSUs wired for this)?

Thanks!