I prefer wraps for newborns because most MT's are way too big & even rolled it can be hard to make sure the baby's breathing isn't obstructed. That being said, I made a newborn MT for both a friend & myself that was really nice, but even if they made them that small, buying one would be kind of silly since they're only good for a couple months (or not at all if you have a large baby).
A lot of people really like MT's for newborns, though. And if you're good at rolling them, they can be a decent option (my rolling always seemed to come undone, which is why I don't like them for newborns). With a newborn in a normal MT, you have to make it short enough for them & keep their legs in, in a "froggy" position, usually for 2 months, until they fit better. You also need to tie behind their back instead of under the bum to close up the side gaps & keep them from slipping out the side.
I hate stretchy wraps, though. I used one briefly with ds2 & switched to a gauze & a woven as fast as I could.
For strap length, 45" seems really short for top straps. My bottom straps are close to that length & my top straps are around 75". I am very fluffy, though. I believe 60" is an average length for top straps, with 30" being average for bottom straps.