I'm looking for performance and reliability. I've noticed differences in Size and Bit. Would it be better to go with 2GB x 72 or 1G x 4?
"x72" and "x4" are referring to different things...
(x64 v x72): 64-bit (non-ECC) v 72-bit (ECC)
(x2, x4, x8): dual-rank, quad-rank, 8-rank
RDIMM (registered DIMM) are all ECC (x72), and it doesn't quite matter how many ranks because single Xeon E5 supports total of 64 ranks per CPU. it only matters if you opted for X9DRI-LN4F+ board (24 DDR DIMMs, 12 per CPU), then you would need to choose "x4" (quad-rank) modules so that you can fully populated all 12 DIMM slots.
actually, you rather choose SuperTalent W16RB16G4S: http://www.superbiiz.com/detail.php?name=W16RB16G4S
why? because it's indeed Samsung original module with SuperTalent sticker over Samsung sticker, but it will be covered by SuperTalent's 5-year end-user warranty.
keep in mind that Samsung or Hynix original modules are all "OEM" modules which don't have any warranty extended to end users, and they would be covered by "vendor" warranty only. SuperBiiz offers 30-day warranty only for the modules you linked.