A twostroke on a tuned pipe is best for high speed dive when you really push the airplane and punish the engine at WOT and it sounds as it gonna explode any time Small sized twostrokes on a muffler just makes annoying sound and usually are low on power Twostrokes are also durable and less expensive on a trainer for newbies doing bad landings every other flight. For everything else fourstrokes are preferable IMO.