Timig light

[dub-disaster]

Going to buy myself a timing light just wondered if it was nessecary to have one with adjustable advance ? The ones without advance are a quarter of the price, don't wanna buy more than I need really as Im likely to only use a it a few tomes here and there, I have got a normal non g40 bottom pulley and cambelt cover with the non g40 pointers on it do I need a gun with advance ? Anything else to look out for when buying one ??