even though if we use the LACP and IP hash, it is not 100% sure the esx will use both the nics, becuase you need to have different hashes for the source and destination IP. That is why the LBT is developed by VMware.
It is available in the ent+ license. In the ether channel or what ever aggregation type, the ESX dont know if the pNICS are congested or not. But in LBT , it will only move the netwrok traffic when the send or receive utilization on an uplink exceeds 75% of capacity over a 30 second period. that is load-based teaming (LBT) policy is traffic-load-aware and ensures physical NIC capacity in a NIC team is optimized.
so the bese load balancing and true one is LBT
refer the below for more info
http://frankdenneman.nl/2011/02/24/ip-hash-versus-lbt/
http://blogs.vmware.com/performance/2010/12/vmware-load-based-teaming-lbt-performance.html