Scootersisters - You may have parted ways with Hitec about the time they started making 1/8 servos that actually hold up. The old 5925/5945 servos felt great to me in the car but they rarely lasted more than one race.
The 5955 feels better and I do not think I have seen one killed yet in the last two years.
As to the digital vs analog question. I find the analogs to feel softer (smoother) initially and then about the same as you continue through the throw. I have also noticed an Airtronics .10s servo is no faster than a Ko/Jr/Hitec/Futaba .13s servo. In fact the Airtrix will usually feel slower when you initially turn the wheel and will feel normal once it is moving.
I would suggest picking analog or digital and not switching back and forth. I think once you get used to one or the other either will be as good on the track. The only thing is there are almost no good analog servos left so you are pretty much stuck with digital I think.