mix it up, run both. personally i get bored with ifmar starts at times, so i would like to see some weeks run ifmar and other weeks full on mass start. mass starts are hectic at times, but its fun. i think club races should be mass start, and the races like roar races, or nationals, etc... or the MORL races, those should be ifmar qualifying.
For Stadium carpet racing in Grand Rapids some of us were getting tired of all the IFMAR starts so we have been doing both heads up and IFMAR starts for the qualifiers (usually 2 of each style with 4 qualifiers total). Then we obviously run a heads up for the Main race. Personally the IFMAR starts were getting to be a drag because you don't get any practice heads up starts to learn from. It seems like the more heads up starts a group of racers do the better the whole group is getting through the first couple of turns cleanly. This "practice" has made the heads up start of the Main race much better over time as the group of racers have learned that you cant win a race in the first corner but you sure can lose one.