Just a matter of size - 90mm versus 125mm - but size is important. Since the main factor in telescope
size is diameter of the mirror or lens - not the magnification or power - a larger scope is a better choice if you want a scope that has potential to maintain an interest in astronomy. A small telescope
can see exactly the same TYPES of objects - moon, planets, galaxies, nebulae, star clusters - as a large telescope, it just can't see as many of them or as much detail in them as a larger telescope. If you are concerned with performance, buy the largest telescope
you can afford (not the one that advertises the most power) that has all the features you want.
Not to worry, any of these are portable. I can pick up an ETX-125 and carry out the back door.
The Nexstar 5SE is a Schmidt-Cassegrain. Won't have quite the tack sharp images of the ETX 125, but will be close. Being a Schmidt, it also has more photographic accessories available.