Don't waste your money to prefer park at Magic Kingdom.
Magic Kingdom doesn't truly have any benefit to a preffered parking pass. You will still need to take a tram which is free or experience a rather long walk from your car to the ticket booth where you will go through security and enter either the monorail line or the boat line to get to the park.
Transportation station doesn't truly offer any real benefit to prefer park because if you park out in the boonies, you still get a free tram to take you to and from Transportation Station so your not walking a long way like you would at other parks.
The best lot is by far EPCOT which puts you right up front to the main entrance. EIther on the left or the right you are guaranteed to be inside the first set of lots in front of the partition creek and trees. At Hollywood Studios you will find your spot on the side where the Skyliner is and that makes for a quick walk from that Skyliner should you be heading back from a trip to EPCOT in the latter half of the day. At Animal Kingdom, you will be just behind the bus loading and unloading.
In every case but Magic Kingdom, you are cutting down a lot of extra walking that most don't want to do as their day winds to a close.
Now, if you are one of those late day arrivers, you can take a risk of not getting the extra parking perk. In many cases the parking cast members will fill in the spots that have been vacated and at times you can slide into a front spot but not always. It is a risk you can take and maybe win.
On our last trip to Orlando we decided to try out the preferred parking at all four of the parks and it was clearly beneficial for this family of 6 except at MK. So the next time you go, think about adding on the one early day benefit that will bring you late day joy and then thank yourself!