How exiting!!
I would choose the bigger female too,if you want to breed her she should be at least 6lbs+ to do so,so bigger is better in this case
Your male could still put on another lb (or maybe not),but even so he is still very little so dont worry about that.There is really no real way of knowing what they will weigh as full grown adults.Lady stopped growing at about 4 months old and at 2 years old she is under 2lbs and has been that way ever since then.The rule of thumb didnt work with her although it did with my other yorkie Jess.
Congrats on your new adition