Its never easy to answer these direct comparison questions.
Its what works for your configuration thats best.
Give Kerio ago if you think you may like it better.
I rate kerio highly, kerio is very popular, more so than sygate it seems, draw what you want from that it, i base that on talk in forums and newsgroups, also the DSLR forum poll.
Kerio, as ive stated before in the forum (search) is very small indeed, the process and driver are small, fast and efficent and change in resource usage / system performance is very minor indeed (i did not notice a change in terms of performance, again search for regarding the process and driver resource usage).
Edit: Ooo, when i say search its above in this thread! We talk kerio so much i loose track
