In my experience there a pros and cons to either sow or boar pairings.
In my personal experience most of my boar pairings have been more stable once they settle past the initial bonding period and/or teenage phase, whereas some of my sows can get quite moody with their cage mates when they go into heat (not all of them, maybe about half of all the sows I have owned have been at least a little moody with their cycles).
However when my boar pairs have had issues it has been a lot worse than when one of my sow pairs have issues, I have had two serious falling outs with boar pairs (blood and injuries) but never with my sows. Of those two major fallings out one boar pair was able to be re-bonded after some time away from each other and they never had any other issues (the initial falling out was my fault after mixing up two items during cage cleanings I accidentally gave them an item that had been in the sows cage), the other falling out happened during the teenage phase of one of the boars and they were never able to be put together again.
Boars can get boar stank, but this can be minimized by leaving an item that is "dirty" in the cage so the area still has some of their scent when you clean the cage. Boar stank doesn't usually linger either, in a well ventilated room it might only hang around for half an hour after they do it. Not all boars have a strong scent to their boar stank either but that is very much an individual guinea pig thing that you can't tell until they scent mark. Sows will also scent mark but they usually don't have much of an odour that we are able to smell.
Sows also have a downside too, while their scent marks may not have much of a scent, they will spray urine when annoyed. So if you have a sow in heat pestering her cagemate urine can be sprayed everywhere, so having extra height to the coroplast walls where it is facing your actual walls helps minimize how much of this urine gets sprayed out of the cage.
My boars are not territorial with their bonded cagemates at all, neither are the sows. I don't really see much dominance behaviour at all in my mature boars with their established cagemate, once they settle they tend to know where they stand with each other so they don't feel the need to reaffirm it all the time (this is not true for when they are young though). However if something big changes I might see the dominant boar rumble strut and mount his cage mate a couple times but they do settle again quite quickly if the submissive boar doesn't put up a fight about it. I do see dominance behaviours a lot more frequently in my sows but that has more to do with their heat cycles then anything.
However my boars need a bit more maintenance around their genitals, I check their penis and anal sacs for any caught debris every week at weigh in time, but only clean as little as absolutely necessary, more often than not they are fine to go back to their cage without any cleaning but they do occasionally get some fur trapped around their penis or some hay and hair in their anal sac (keep in mind their anal sacs have a natural secretion that acts as a lubricant and you should leave as much of this as possible, this secretion also stinks and is part of what makes boar stank as they will flip their sac inside out and drag it on the ground to scent mark).
All things considered in my opinion either boar pairs or sow pairs are just fine, it would be better to see if you can go to the rescue and meet some in person, see if there is a particular guinea pig that has something about them that you like. You won't be able to tell the temperment of the guinea pig from photos, and sometimes the personality of the individual guinea pig can make a big difference.