ExpoDev for iOS is different from the version for Palm devices in many ways. Fundamentally, they accomplish the same thing – calculating accurate exposures but they do so in slightly different ways.
ExpoDev for iOS is a bit more accurate when calculating exposures in two ways: Internally, ExpoDev for iOS uses a more accurate representation of aperture values than the Palm version did when calculating exposures. This new version also rounds exposures as needed in slightly different ways. An exposure is rounded (to the nearest 1/6 of a stop) any time that the exposure calculation produces an exposure that cannot be physically set (for instance, if the calculated shutter speed is not a standard value, e.g. 1/12th, 1/287th, etc…). Because of these differences you may find that the two versions do not agree when compared directly. In most cases the differences will be slight but in all cases, ExpoDev for iOS is the more accurate version. As a consequence though, you may find that ExpoDev for iOS has a little less leeway for user introduced metering errors.
The Depth of Field calculator is also fundamentally different than the version for Palm devices. Besides offering additional ways to calculate DOF, it is a completely redesigned version that allows the user to specify the level of sharpness desired (via the Circle of Confusion app setting) and gives the user additional information such as the Optimal Aperture calculation. As a result of these changes, the DOF calculations between the two version may differ significantly as the Palm version used a simpler model for calculating DOF.
Other minor differences include allowing the use of an expanded range of EV values (Incident metering only), using named filters with user defined factors (vs. using a plain filter factor value), an option to favor DOF whenever an exposure needs to be adjusted.