I'd say a small hand luggage, it's easier to keep things organised that way. It's what I'm planning to use too since I had a backpack last time and your same problem
I had a medium suitcase my last pregnancy, but I didn’t take a bag for baby I just put it all in one 😂x
Also, something I did that was recommended in my antenatal class, was to do a little ziplock bag with baby's clothes, hat etc for after delivery and label it " for theater", so it's easy to find in case you have to be rushed for C-section, or even if not, and someone else has to look in your suitcase.
I took a 2 x bags with my first but with my second I’ll be taking a small suitcase with wheels as it will be much easier to move around! Then a small bag for baby.
I’m going to take a small carry on this time. It’s got wheels and plenty of space as well as different compartments.