The most important thing to note about data rates, which applies to both the DSM and OBDII version of PocketLOGGER, is the fact that the data rate displayed is total data rate. In other words if you were getting 50 samples per second, and were only logging one parameter, then that one parameter would be logged at 50 samples per second.
But say you log 10 items. You still get 50 samples per second, but now those 50 samples have to be split between 10 parameters.
Total sample rate / number of parameters logged
= Samples per second per parameter.
50 samples per second / 10 parameters logged
= 5 samples per second per parameter
In this case, each parameter is only being logged at 5 samples per second. This is not such a big deal for DSM users, but OBDII users, where the total data rate can be anywhere between 6 and 20 samples per second, logging a bunch of parameters at the same time can make the data collected useless. Logging 6 parameters at 6 samples per second will give you 1 sample per second per parameter. Seeing your timing once a second is obviously pretty useless. A lot can happen in a second.
DSM data rates can reach over 70 samples per second when the car is not running. The problem is as the ECU gets 'busy' running the engine (firing plugs, opening injectors), the data rate will decrease. Typical data rates at redline drop to around 50 samples per second. Depending on the PDA used, as well as the car and year, your maximum data rate may be slower. But in the end, it's the ECU that limits the data rate when it's most important (when the engine is running) so don't be concerned about getting a 'faster' PDA.
OBDII data rates vary between 6 and 20 depending on the car. PocketLOGGER's unique Byte Timing controls allow the user to optimize the data rate no matter what car or PDA you have. The worst car we have found is the Subaru WRX which can barely maintain 6 samples per second. Most 98 and newer cars (of the ones compatible with PocketLOGGER) can get rates in the teens, with some hitting 20 samples per second.
Check out the data rate chart