First of all I must say again, if u got the budget just go for the SB800..dun regret like me where I got only a low budget and buy the SB600 now end up regreting for not saving more to get the SB800.
As for the advantages and disadvantages, many CSers has already given many..but just to summarize for you, I list them down again..
Pros of SB600 over SB800 - One and only one and that is the price..
Pros of SB800 over SB600 -
1.) Support more modes; TTL, Auto, Multi-Flash/Strobing, Manual Flash
2.) Higher GN, which means more powerful
3.) Provides diffuser dome(omnibounce alike), bounce card(too small, u definitely need to DIY a bigger one), color gel(cheapo type)
4.) Can act as commander, good for bodies like D50 where commander mode is not available on the body
5.) Give more control in manual mode 1/1 - 1/128, SB600 only can control from 1/1 - 1/64
6.) Support SD8A, additional battery pack for faster recycling time
7.) Support up to 105mm focal range, SB600 only support up to 85mm..actually this is factor due to GN..
8.) SB600 rubber cap confirm drop, SB800 never heard any user complain before..
Most of the time flashing using TTL mode or Auto mode is rather accurate for a newbie, and the control u need to adjust is +/- on the flash itself..
The formula for setting the aperture is useful only for Manual mode..tough one, still learning..:sweat:
Enjoy flashing!!