To be honest the one night a week that there is only one arena has some of the worst gameplay that I see the whole week.
Bigger hordes, more base sneaks, etc.
I for one am not a big fan of the one arena idea with one exception, I do think the offhours arena implementation has worked well. Even if it means a slight interruption in gameplay for the minute or so it takes to log into the new arena at switch over.
Just my $.02
Besides the only one who knows what the numbers are for players is HTC and I have found no reason to dispute their claims that the numbers had begun to sink dramatically until the arena split took place. Honestly, I can see why it is the way they claim. If it were not for the fact that I am limited on the nights I have to play, I would probably not play on Tuesdays.