Dave, interesting question. Numerous variables involved in my opinion. Personal choice of course, but lots more which change with time and modelers age/experiences. Where one lives, city, rural, conjested areas..various laws, ordinaces, hazardous substances, eg dope, fuel, litigation issues, areas once vacant with no rules now used for other purposes, or you get chased away. Perhaps unruly youngsters nearby, limitations in some building supplies...old school methods limited, costs up, toxic odors/alergies, hobby shops limited, some poorly supplied and not always user friendly.
How about living conditions...own a home with private grassy areas? Nice neighbors? Have a family, spouse, a place to build without worrying about strong odors, making a mess, or storing "stuff". You're gonna have a mess, sawdust etc....hopefully, modeller keeps area neat and keeps paints, razor blades etc out of little ones reach. What does one do with finished models...store indefinitely, donate, sell,...flying models take up more room than static plastic ones. Or, do modellers pass 'em down to kids? yours, others? Will they share your enthusiasm, past, present?
In my decades of interest, I've been thru lots of these variables. Given a choice of ONLY ONE, I'd select Flying Model... conditions permitting. One learns more with this and can apply it to many projects. Construction builds not only an airplane, but teaches various skills....and if the thing gets airborne, wow! .... a rush of sorts which will not be forgotton. Its likely to crash at some time, or get chewed by the dog, or get stepped on, while the plastic one may stand proudly on a chest of drawer maybe, longer, but gathering dust. This is not a really a put down on static/plastic models....they are part of the experience, and valuable lessons can be learned, matching up pieces, painting, lining things up, etc and proudly displaying a nicely detailed model.
I see I've consumed too much coffee this morning but felt the need to yak a bit. Given the two, I'll vote for Flying. For, in the classic sense, using traditional balsa, it involves building...in itself a great way to learn, also modifying....to fine tune things with the flying itself. Hey! did it fly...even if a little? Congratulations. Did it not? Don't give up. You learned a lot building that plane....and you're gonna think about the experience for a long time. Some day, you may want to build a flying model again. They're pretty good for any age. I guess many of us may select something midway.. some static, some flying. That's ok...but do try to get your kids involved in this rewarding, educational hobby.