[Spaceships] Your preferences regarding plausible/playable Reactionless Drives

[jason taylor]

What I'd like to know, is whether reactionless drives really get enough plot mileage to justify the bending of normal physics from the authorial stand point. How much do they do that another kind of reaction drive does not? If the idea is to economize space or fuel or reduce heat then ano ther kind of reaction drive can be arranged that does the same thing. FTL is an absolute necessity(space opera never seems to work without FTL, so we just have to live with it). Grav control is very much of a convenience(there are only a few times we really want to think about the yucky consequences of being without gravity for weeks at a time, and anyway it's an extra headache for the props department in a stage rather then literary forum). But why reactionless drive?