Bidvertiser sucks. They don't pay well and their "context targeted" ads aren't targeted at all. They do pay every $10 via paypal and that's the only benefit to using them. Adsense is $100. But, honestly, if you aren't making at least $100/mo with Adsense you are doing something wrong.

In conclusion, use Adsense.

haven't tried Bidvertiser yet. Is it true that it's possible to have it along with an Adsense on a same page?

No, Google says you can't have ads that look similar to Adsense ads on the same page.