I've L920 , i need another sim card ,should i go for L730 or get L640xl despite of its poor material?
Depends. If you don't mind the larger size the 640 XL has better specs in general. If you want a smaller phone, grab the Lumia 730.
Size also matters (i prefer 730 size) ,but i concern about quality ..is 730 same as good quality of L920 ??
Well the Lumia 730 and 640 XL both have removable backs while the Lumia 920 does not, so some would argue that the Lumia 920 has a nicer build quality. However, both the Lumia 730 and 640 XL have very good build quality. I'd be inclined to tell you that the Lumia 730 may be the tiniest bit nicer.
I may go to L730
Just remember the disadvantages:
The Lumia 730 is older. This isn't necessarily a bad thing but could mean the 640 XL will get updates first.
The 640 XL has over twice the megapixels and is, in general, a nicer camera.
The 640 XL has a nicer screen. Yes, the Lumia 730 is AMOLED, but it also has a PenTile pixel sub-array that makes the screen seem fuzzy, even though it's smaller than the 640 XL.
The 640 XL has Glance I believe.
I think i'll repeat thinking again after your qoute thanks a lot for your help