Lots of variables in that like you said
, as if you fill your space with one plant it is going to take longer in Veg to fill said space, if you growing Regs have the issue of putting a lot of time into a Male whereas Fem seeds less likely but Hermies can have same effect to a point. So it's kind of a "too each their own" and "your results may vary on your driving habits/conditions" 
. I'm a glutton for punishment so rarely do I not have more than one strain going at a time, so deal with all the challenges with them having different wants/likes/how they want to grow, so that can factor in if you just want to focus on one strain then just one plant may get you more than two (or it may not as you putting all your eggs into one basket so to speak). Try both eventually and you will get a better idea of what works best for your style and what is most productive for you or makes the most sense to you. Just remember "change likes to rear it's ugly head" when ever it wants to or it feels you really need to adapt once again as you are too complacent for it's liking , which throws a wrench into your whole "system" you have come up with that "works for you".
