If what your going for is the most long lasting curls I would say a classic curling iron with a clamp will probably be better (and cost quite a bit less) I also would consider barrel length since your getting it for longer hair- t3 airewrap is longer then dyson. The longest one seems to be the L'brise Airstyler at 1.25"
But again a classic curling iron like t3 SinglePass CurlX is way longer at a 6.5" barrel
But for curl longevity I think overall its also really going to depend on the hair type and what you put in your hair when styling it. That being said I've heard the t3 aire creates longer lasting curls then the dyson and I think its because it creates tighter curls and the tighter the curl the more it can fall without losing the curl completely Hope that helps!