HT on or off for E5-26xx ?

I'm bringing up a new type of server using Intel E5-2620 (unisocket)
which was selected for good SpecIntRate performance vs cost/power (201
for $410 and 95W).

Was assuming it was 6-core but I just noticed it has HT which is
currently enabled since I see 12 cores in /proc/cpuinfo

Question for the performance experts : is it better to have HT enabled
or disabled for this generation of Xeon ?
Workload will be moderately concurrent, small OLTP type transactions.
We'll also run a few low-load VMs (using KVM) and a big Java application.

Any thoughts welcome.
Thanks.