Performance Drop from Version 1.x to 2.x ?

Forgive my poor English

cocos2d version : cocos2d-x beta3-x-2.1.1
device : htc g7

just add a full screen image ,the fps drop to 50

but i download the test appliaction [http://www.cocos2d-x.org/attachments/111/cocos2dx-test.apk]
run “TracnsitionsTest” fps can stabilize 58

and then i try to release build [cocos2d-x beta3-x-2.1.1] TESTCPP project ,run on my device(htc g7),also performance is worse (fps 40~43)

who can explain the result!

thank you!