Well am on the nexus 4 currently and having to deal with the damn wakelocks and people are like either disable the application or delete it which is stupid because yano what if I want to actually use it. How did the N9 keep the cpu awake? or get out of deep sleep, while still being a full multitasking OS and not dent the battery life so hard.

I remember that Felipe's blog post gave some insight into that:

Android vs. Maemo power management: static vs. dynamic by Felipe Contreras

I don't understand the question, AFAIK N9 does not ever go to deep sleep, how could it since it needs to be connected to network.
Or, what's your definiton of deep sleep?

I guess, he means something like:
you set an alarm to wake you up in the morning and then turn the N9 "off". It will turn on and wake you up in the morning.

or what he means is how N9 can keep full multitasking with reasonable response (refer to cpu awake?) and minimum battery impact while n4 (nexus 4) needs to disable or close the app to keep battery life reasonable.

I think it's all about power ( and memory as well if referring to multitasking?) management that thp has mentioned.

Regarding to the android, OP may want to try an app called Greenify. It can "greenify" apps you want and put into hibernation while not used. It can somehow help to save some juice and memory (RAM)

thp hit the nail on the head. I've tried greenify but whats the point of an application and push updates if I can't use them.

battery life on both of them is fairly similar. But since the nexus has a bigger battery I expected more from the bugger.