Or do they work differently.

thats a really great question. as i have mines registered to the mobile me find my ipad also. i rhink they work differently from what ive been reading. the untrackerd clears that secret location file continuosly. i believe the mobile me thing actually activates or uses the gps coordinates. there is a seperate file for that. that secret file all over the web n news isnt used at the moment. it only stores the info. plus its not even encrypted so basically anyone could get access to it. they say it might be for some future ios5 feature or for advertising purposes. even still, i dont want all my whereabouts tracked or stored into ipad. that info in the wrong hands wont be good. someone else hopefully will chime in soon on this issue. good question though.

The two are unrelated.

FindMyiPhone actively determines the location, when you ask for it and uses the Internet connection to broadcast the devices current location, it doesn't use the location file, which will be deleted by untrackered. Untrackered deletes the history of where the device has been, but that history never gets transmitted anywhere.

Can anyone with untrackered installed comment on if there is any noticeable hit on battery life?

i have it installed and no neg. effects on battery. it actually shouldnt make any diff. ive also installed the auto location tweak. which auto matically turns location services off n on when needed or when an app requires it use. seems like my battery is lasting longer with that tweak. cuz b4, i had my location on 24/7. evwn then, my battery life was great. now it seems to be even better. if i start to notice a faster battery drain with untrackerd, then ill uninstall. for now, everything to be running fine.