i don't think abp performance would differ on 1.5.x versions. it could be related to the subscription itself..when it got updated, it might have gotten too big making kmeleon slower.
disable adp or uncheck the subscrption temporarily and check if it's launching faster..if not, try different abps and see if it gets better
latest official version (1.0.2)
- this version has a toolbar button stuck bug on some systems
- this version has k-plugin memory leak after very long usage but no toolbar button bug
- this version doesn't include a kplugin and substitutes for k-plugin functions with autoit, good for systems with low ram but has no statusbar icon and lacks some features that are accessed from the statusbar icon
- same as above but based on 1.0.1
you can do dirty(on top) installs with all those versions without problems, your subscriptions and prefs will remain intact because they are saved in prefs and your profile folder. the unofficials disable the k-plugin by default even when it isn't available so it's better to test them last, you can always reenable the k-plugin adblockplus.dll from kmeleon preferences>k-plugins