YouTube is monetized with Adsense. Even if you partner with a network, you are still using Adsense, you're just using the network's account instead of yours.
If you monetize the "regular" way, YouTube/Adsense pays you directly.
If you sign up with a network, YouTube/Adsense pays the network, the network takes 20% or 30% of your earnings and gives you whatever is left.. In return, they promise you a bunch of stuff that probably is not worth it.
The CPM varies based on a bazillion things, including factors like weather and the phase of the moon - but it will vary regardless if you get paid directly by YouTube/Adsense or if you get paid by a middle-man network.
Basically, most networks just take your money and do not give back a lot in return, so sticking with getting paid directly by Youtube/Adsense is probably your best bet.