I'm 6'5" and have spent lots of time in a 14A in addition to my RV8-FB.
The 14 has more room overall, esp when flown solo. That being said I am much more comfortable in my RV8 with the fast back. The fastback mod gives me more shoulder room in the cockpit and moves the roll bar behind my head. That combined with the view advantage of center line seating fits my mission perfectly. I'm also fortunate that my spouse likes tandem seating, she doesn't have to compete with me for shoulder room and really likes that she has her own space. She says it's more comfortable than the Piper Saratoga we used to fly
There are other considerations as well, build time, aerobatic performance, ease of accessing gear/cargo in flight, always regretting not having an 8 , etc.