Honestly I am not sure of exactly how old they were. Son was first child. I started encouraging him by setting out a potty chair, etc when he was around 2 yrs I think. Maybe 20 months? not sure. Anyway... I didn't push anything but encouraged him to try it out, etc. He didn't have much interest past the initial curiosity at first... but then I started encouraging him more, and got a seat attachment for the regular toilet. He was more interested in that. He was pretty much trained by at least 28 months. At 32 months I KNOW he was fully trained, b/c by then he had already transitioned to standing up. I KNOW that age, b/c I was 6 months pregnant and he dropped the lid on himself and I had to carry him (I was HUGE) NAKED from the waist down through the house and hold him to console him. THEN put shorts on him to drive him to the ER to check everything out! (Will NEVER forget that... USE a STEP STOOL so no seats get dropped!!)
With daughter, she was very interested early on in everything I did in the potty myself. She was the child that was IN the bathroom with me... wanting to flush MY stuff. lol
She was transitioning from wearing cotton training undies to regular little girl panties when she celebrated her 2nd birthday (by the way, also the day she voluntarily traded ALL her paci's for some toys at the bakery). She was amazing! Rarely had accidents (NEVER at night) and LOVED to visit every public restroom she could con me into! lol
So, yes, I think generally speaking girls are easier. But I also think that part of that is because there is NO confusion for them about standing or sitting. I never worried about standing for our son, until he had fully mastered the entire process. Then, my husband said "it's time" ha ha....
I also found that with my son, he would wait until THE LAST SECOND to try to "make it in time" to go pee... he would get very involved in whatever he was doing and didn't want to stop to go use the potty. My daughter never really went through that "putting it off" stage. SHE used using the potty as an excuse to get out of bed after she went to bed for the night... lol.
Oh, and if I had waited until my son woke up dry most mornings, he would have still been in diapers at about age 7. He is a VERY deep sleeper. There are plenty of posts on this site from moms trying to figure out how to help their older child (6, 7, 8 yr olds) get through the night dry... some kids (maybe a LOT of kids) sleep so heavily that they do not feel the "urge" sensations that wake them up when their bladder is too full. And everyone's bladder matures at a different rate also... I think my son had a small bladder and it needed to catch up..add to that that he slept too heavily to notice... voila... not many dry nights unless I woke him up and took him potty at 11 pm before I went to bed myself. So I would be cautious about using waking up dry as a marker for readiness. If you notice that he is doing that, Great. Use it as a marker. If you don't see this happening, don't use it as a reason to wait, either. just my opinion.