It's really hard to say what you would. Trios can be tricky and really depend on the individual rabbits involved.
Females do tend to be more territorial and an established female might not appreciate a new one. However, some females do get along well.
Males can fight, but also tend to be better once neutered. It does seem rarer to have 2 males, but it can happen.
If possible, you can take your rabbits and maybe meet another fixed rabbit of both sexes? This might help to determine if they are more receptive to one sex or the other or have issues with one.
Males are cheaper to neuter than females, so that can be a factor for some people.
Do keep in mind that they might not get along as a trio. It is risky to bring in another rabbit with the hopes of a trio. You can end up with the original pair broken up and one going for the new rabbit. You could also have the pair go against the new rabbit. Just be prepared for a long bonding process and it not working out.
I would decide which sex you would prefer (if the choice does arise) and go for that. If they end up bonding as a trio, that is great, but if not you still have a nice rabbit.
