As mentioned in a previous post, the antibody of choice for phosphopeptide enrichment via Filter Aided Capture and Elution is the Millipore 4G10 antibody.
Recently, however, Millipore has introduced its new 4G10 platinum antibody. Due to a slight order mix-up, we ended up with aliquots of both the regular and the platinum antibody.
Instead of having 2 separate antibodies around, the sample was split and enriched by equal aliquots of the two antibodies, with essentially no change in peptide enrichment.
The 4G10 platinum was developed to minimize lot-to-lot variation, but if you are not concerned with variation (i.e., you are doing 1 enrichment), save yourself $120 and just get the old 4G10. As far as lot variability is concerned, I've never had a problem with a millipore antibody and if they have variation between lots, my guess is that it is going to really affect 1 in 1,000 experiments.
Summary: 4G10 vs 4G10 platinum? 4G10 is cheaper but may vary to a level (I'd guess is imperceptible) between lots.