By being able to change element lengths, the SteppIR can maximize the gain for its boom length easily. Play with 4NEC2 and you'll see that for any given boom length you can achieve the most possible gain by changing element lengths. The SteppIRs allow you to do that. But...about half the hams I know with SteppIRs have had to service them within the time they've had them. That is a possible disadvantage if you don't have a system that's easy to service. In some cases, it means a crane and dropping down the antenna to ground level for service (due to moving parts). When you have moving parts, just like a car engine, service could become an issue.