So here's the report:
Went with the suitcase and rolling briefcase. No issues at LGA, though I gate checked the suitcase to make people's lives easier.
At return at ORD, agent in front of security blocks my way and insists that I check it. Other agents told me that the size is fine, though he insisted. I begrudgingly checked it and paid $25 and sent an immediate email to American demanding a refund.