Noob Query re. phased v. continuous-play mode

[neonlicht]

The JTS operational games have the option (available via the "Rules" dialog) to play scenarios in Phases: i.e. "Manual Defensive Fire", as opposed to a continuous mode (i.e. no phases, with freedom to move or fire at will etc).

As a new and inexperienced player I was wondering: what are the pluses/minuses of the two modes, and which is more popular? 

Also, which is best (or recommended) for single-player scenarios?

Does it, in fact, matter much?

Many thanks in advance for replies. :-)