Having external finder is an advantage? Not for me! I hate those things. LTM - well I deal with that if i really like the lens, like, for instance - Nikkor 10.5cm/2.5., but I still hate dealing with ltm adapters, as most of my cameras have M-Mount - I prefer lenses with M-mount. So, those wouldnt be advantages for me, as they are for you.
Plus price-wise and image quality-wise - for me hexanon wins - no questions. The only thing about Pentax lens is - it's rarity. Not to say its a bad lens - it's not, but I do not believe its worth the trouble other than collector's item. In any case - hope you will enjoy yours and post some pics from it. Who knows - maybe it'll deliver wonders in your hands and I'll change my opinion of it? 😉