PRO has better backup compatibility. ME has support for archaic 1.50 homebrews.
From what I got from the changelog, they've fixes the cIPL issues now too.
fate6 wrote:well its designed more toward the 1k & early 2ks while IMO PRO is really more for the newer PSP's (especially with the online)
Pro online on the 1k isn't completely impossible. Also, ME was made to have leda (archaic homebrew) support, not just for the older PSPs. Pro was made as a general-purpose CFW.
fate6 wrote:PRO = HEN
ME = CFW
HEN = does not install to flash, gives (limited?) homebrew/pluging/(ISO?) compatibility, not permanent. Example: ChickHEN (5.03)
LCFW = installs to flash, gives homebrew/plugin/ISO compatibility, not permanent. Example: LME (6.60)
CFW = installs to flash, gives homebrew/plugin/ISO compatibility, permanent. Example: M33 (5.00)
fate6 wrote:you are right LME would also count as a HEN in my book
perma patch is just a auto booting HEN
and as for CIPL... well I would say thats a CFW but.... hmm >___<
(we really need to start some sort of standardisation)
Perma patch = auto boot by swapping a prx file in the firmware
cIPL = auto boot by installing some custom IPL code
Umm, difference please? And standards?

Not a chance you are going to get your standards accepted by everyone, so just go with whatever things are called.
// On-topic: those are bug fixes.