Why slower than libgdx ?

cocos2d-x C++
#1

I originally thought cocos2d-x should faster than libgdx.
But after test drawing the same image(40 * 45 in 64 * 64) on Sony Ericsson z1i. In batch mode cocos2d-x slower obviously. Why?
The fps of result list here.

number of sprites …………. 1k ………… 5k ………… 10k ………… 50k
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cocos2d-x immediately mode …. 34 ………… 6.7 ………… 3.3 ………… 0.7
cocos2d-x CCSpriteBatchNode … 60…………. 18.3 ………. 9.6 ………… 2
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libgdx immediately mode …… 27.8 ………. 6.17………… 3.1 ………… out of memory
libgdx SpriteBatch ………… 66.7………… 33.3 ………. 16.7 ………. out of memory
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#2

Interesting question.

#3

I think that cocos2d-x limits fps to max 60 by default (at least on some platforms).