Rotary shavers do handle flat-lying and randomly growing hairs (more commonly found on the neck) better than foils. You'll also likely find it shaves slightly less close than your Arc 4, but this Norelco has the "ComfortGlide" rings which for me actually do provide a more comfortable shave (it will also be considerably quieter). So there are tradeoffs with any model, but the 6800 is a great shaver and will probably improve your shave if you're having problems shaving your neck. The caveat I would add is it usually takes a little longer for your face and beard to adapt to a rotary compared to a foil in my experience (Philips says two or three weeks), so persistence pays off. Good choice.
If you like a foil shaver except for the long neck or flat lying hairs, you might want to try a Braun 7 series shaver. Braun shavers get good reviews on handling longer hairs for a foil shaver.I agree, the Series 6000 is good shaver and also has a good price to performance ratio.