A long inseam for your height might suggest the smaller size frame. However without trying them out for real and riding them in the conditions you normally ride, the best thing you can do is accept that you won't know for sure. However neither size will be so detrimental to you that you can make it work. What will be detrimental, is if the bike isn't made in the geometry for the position you wish to be in.

Relaxed geometry doesn't mean you will be relaxed and comfortable on the bike. It just means you'll be more upright than you would on a race fit geometry bike. More upright isn't a guaranty of comfort for everyone. A person that likes to ride with a all out adrenaline rush 90 minutes to 3 or 4 hours and on a unloaded bike, might be more comfortable on a race fit bike than if they were on a relaxed fit bike. Conversely, one that is having to carry a load of camping gear and stuff for a extended trip will probably be riding at a much slower pace and therefore might be more comfortable on that relaxed fit bike.