I'm thinking of buying either; Essential Chess Openings: The Complete 1.e4, by Stefan et al, or Understanding Chess Move by Move by John Nunn, anyone have or read either? and, arbitrary I know but the better book?

I would recommend Understanding Chess Move by Move by John Nunn.

 

Read the customers reviews in amazon.com. 

I have read Understanding Chess Move by Move, and I would also recommend it.

If by "better book?" you are asking which one is better - it's impossible to say. They deal with completely different subjects.

i havnt read either but i would recommend "attacking chess"

I would recommend getting separate book on particular opening (if you up to studying openings) and study it from cover to cover. I  don't think it is possible to put all the opening  systems against o with 1.e4 in one 200pg. book.  I have  separate books  on Sicilian, queens gambit,  Spanish, Catalan, scotch, English, Karo-Kann, etc. It takes more time to study such books and they are typically harder (higher level chess), but it really pays of during tournaments! 

 Hope that somewhat helps.

www.thechessworld.com 

BTW is that book by Steffen Pedersen, the Danish IM?? He is a good author and chess player.

Thanks for the suggestions and comments, I've just bought the John Nunn,