Hmmm tough question there. I too love Webers for their versatility, and always say if I cold only have one cooker it'd prolly be a kettle. However I own both so I never really thought about which one would win out in a contest. Honestly I like the Akorn for it's own uniqueness and the flavor it imparts with burning lump, and it's ridiculously efficient too. I don't really smoke in my Akorn since I have an UDS, and a horizontal drum smoker, and I don't want everything I cook on the Akorn to taste like smoke like it will if it's used as a smoker(when the smoke seasoning burns off while grilling). I look at it more as a grill/roaster that has it's own application and flavor characteristics(see lump coal). On the other hand, you mentioned ash buildup in your Weber; have you considered using lump in your kettle instead of briqs? I've found there's prolly 1/10 the ash buildup with lump vs. briqs. The Performer does have some nice features like a table etc., but the Akorn also have shelves, extra cook rack etc. plus a cast iron grate is an awesome feature to have standard. You can also make a "one touch mod" to start your coals if you're a little handy with a torch and solder. If I get a chance I'll post a pic of this mod.
They're both great cookers...
Guess after all that blathering I can't really answer your question, but if you're keeping your kettle and adding to the "family" I'd say get an Akorn. That's just my opinion, man.
UDS'-55&16, Akorn, Bar-B-Q Kettle, Drum Grill, miniWSM, cobweb-covered gasser. I'm JD.