I agree 100%. I would go with the cheaper (in dues). Having ALPA or not will simply not make any difference. The only way you will get a contract is strike (it will take you years just to get released) or after Franke has cashed out after the IPO. That too will take you quite a few years.
ALPA is good if there is a merger with another ALPA carrier. But a merger is unlikely until after the IPO. Unless Franke gets paid the same as the IPO would bring him. That might happen.