Samsung Galaxy Mini S5570
Sony Ericsson Xperia mini [AP set]
Sony Ericsson Xperia X10 mini
won't easy lag..?

it depend.. ,

anyway, i would recommend Nokia N9 

it is true, iPhone 4S[especially] wont easy lag, but you have said that you dont like that, so.. I would suggest Nokia N9..

but then.. Nokia N9 may not have so much apps,.. anyway.. you can refer to --> http://forum.lowyat.net/topic/2066795

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Added on January 28, 2012, 11:45 pm
hardware wise..?    very hard to say, technology advanced faster nowadays..

anyway, what is your need and usage...?

I can't help you if you just state your budget.. and then say the best bang for buck , 

maybe I could suggest
->

Sony Ericsson Live with Walkman = RM 590[AP set]
Android 2.3 , planned to be upgrade to 4.0 , 1GHz processor, with Adreno 205 GPU , GPU quite okay..,

ya haha
SE xperia mini ap set
but screen just 3inch only

Xperia Mini @ 530 ap