I prefer the regular Syringe Gun because of its health regeneration rate. If it gets to the point that I need to fight, things are already a mess, so I'll be hack-and-slashing my way out with the ubersaw.
Kritz is great when you are supporting an able player, but 90% of pub players function better with an uber. Exception: I play all highlander games with Kritz. The faster charge rate is essential.
Between spies and random close encounters, I've found that the ubersaw can lead to repetitive ubers with little downtime in between.