T4 DNA ligase - (Jun/01/2007 )

which T4 DNA ligase is better to use from the New england biolabs. Following both are the same price but different in units concentration.
Normally which one is better to have higly concentrated or diluted T4 DNA ligase. Both have the same price.

M0202S 20,000 units 400,000 units/ml

M0202T 20,000 units 2,000,000 units/ml

This depends on whether you are doing a blunt ligation or not. For blunt ligations, you need high concentrations of ligase, and typically also a PEG containing buffer (the buffer and ligase from the quick ligation kit). For cohesive end ligation, you need much much lower levels of ligase. Even the M202S ligase can be diluted 10x with high activity.