I have the Forster hand held turner - MidwayUSA - Forster Hand Held Outside Neck Turner
I like it because it is economical, has a wider blade than most
and you can also buy an inside neck reamer that will interchange with the outside neck turning mandrel
For expanding for the Forster, I just neck size with a Lee Collet and it works perfect, no separate expander needed.
I have used a friend's K & M and it is certainly a fine tool. The blade was a lot narrower and it costs a lot more, especially if you get all the attachements and cutting mandrels.
The most important thing you will need to make neck turning more accurate is a ball micrometer and a stand to hold it is worth the money
a caliper just won't cut it.
Outside neck turning is not necessary with factory chambers. I have 3 tight necked chambers that all require that I take off brass in order to get the recommended .003" clearance around the neck. If you don't have a custom chamber tight neck then just skimming the high points off the neck can't hurt and IMO it will decrease the amount of runout.