Depends on you need. What is good for me may not be good for oyu. Spider has one bank of 256K flash only. it's completely solderless on all xboxes. Xenium offers more banks but requires some soldering on 1.6. So here is the choice decision: if you want to have more than one bank on a chip, Spider is out. If you need solderless on v1.6, Xenium is out.
because i found a solderless adaptor for the xenium, and are there any other enhancments on the xenium compared to the spyder?
With Xenuim, you can have two banks of BIOS and switch select which one you want to boot from. Spider has only one bank of BIOS. You either enable or disable the chip. Xenium allows you more BIOSs to boot from. Then, you may ask why whould anyone want more than one BIOS on the chip. Then you probably don't need to know.
Actually Xenium Ice now has a solderless adapter (SP). Look into it and you'll see Xenium hands down is far better than Spider without a doubt. I speak from experience having succesfully installed BOTH a Xenium mod chip and a Spider mod chip. (-;