My personal thoughts on smoke systems:
1. weight - On a high performance aerobatic plane the added weight is not worth it IMO unless it's a large plane (30 to 40 %) where the extra pound or two won't make a significant difference to the wing loading. On a warbird (especially smaller ones) many are already on the heavy side. Adding smoke won't help this. A Cub or something might be fine but may look a little silly with smoke pouring out of it.
2. Reliability - Many smaller glow engines don't run as reliably if they have smoke systems running. Now add an unreliable engine to a heavy plane and you're asking for trouble. Best for a larger engine and plane.
3. Visual appeal - Smoke looks cool and is an attention grabber. With my current skill level I don't wish to draw any more attention to my plane and my flying than necessary.
When I have a 40% plane with a good strong gas engine and my skills have improved dramatically than I will probably put a smoke system in it. But not before then.
