whatever gap you end up with i think there are pros and cons to each.
i have 3 that are roughly 1.5 yrs apart each, and i like the small age gaps maybe just cos that is what im used to but i like the idea of them growing up close and its nice for them to be at similar stages and to interact together (although my older two do drive each other mad at times but can see they love each other, from ds2 being a tiny baby they have been really close).
it can be fairly full on, as it does keep you busy if they are both young and more dependant on you, not at an age for any nursery place or anything but i think its very manageable, it can be nice to be kept busy i think and the plus with having 2 small ones is that if they both sleep during the day then you get to relax
but if i look at my ds1 and ds3 i can kind of get the idea of a 3 yrs gap looking at the interaction between them. i have to say i think it would be probably a more 'easier' gap because age 3 are more independant and able to help you and also because they normally start nursery some time after age 3 so once they do, you would only have one at home again for part of the day, which would make life really easy (well im only presuming that.. cos mine does not go to nursery yet) and if they go to nursery it would give the chance to have plenty of one to one time with your youngest one, which is a downside of having them all close together sometimes you feel they might be missing out? but then the downside of the bigger gap they will be alone without their sibling during the school or nursery day, and your house may feel more quiet and empty compared to having 2 of them at home together close in age, and there will be longer to wait til they get more in a similar stage/age to each other
as for work & maternity leave issues i have no idea..
i would just say if gaps less than about 16, 17 months i would just be a bit wary of the oldest one not being walking yet as seems like that could be a bit tricky logistically? maybe i worry about that more as mine so far both quite late walkers, yours might be walking at a yr so not an issue but its not that rare for them to be late with it, but with mine had the gaps been 1 month less i would have had problems with this both times!