Are you using explicit transactions or only implicit transactions?
As of 5.2, non-transactional caches use a scheme where the modification is sent to the primary owner, which then sends the modification to the backup owner(s). The primary owner waits for responses from all the backup owners, and the originator waits for
a response from the primary owner.
In optimistic caches, one-phase transactions are much simpler: the originator just sends the modification to all the owners, and they all apply it. Execution order is preserved for transactions originating from the same node, but transactions originating
from different nodes can be applied by the owners in any order.
So implicit transactions with use1PcForAutoCommitTransactions="true" can certainly be faster than non-transactional operations, but I wouldn't recommend using them because they aren't atomic. (To be fair, there are also some problems with atomicity of non-tx
operations during state transfer that we're just fixing now - e.g.
https://issues.jboss.org/browse/ISPN-3357)