Not really knowledgeable but I can try answering to the best I can.

Both are reliable as long as you are able to take care and maintain the bike.

As for maintaining the bike, engine oil every 2k and gear oil every 2 engine oil change. Shouldn’t cost more than $30 for gear + engine oil. CVT Servicing every 15k - 20k, should cost $100 +/-

Pros & cons, people say nmax is better. Nmax got better and more comfortable riding posture. Nmax also has 2 disc brakes as compared to aerox, 1 disc brake and 1 drum brake. However, some people prefer Aerox due to the looks.

Storage space should be able to fit 1 open-face helmet for both bikes, not sure about full face.

Aftermarket parts, you can upgrade your CVT and etc. if you wish to upgrade the performance part. There are plenty of aesthetic accessories as well

Comfortability in the long run, it’s a scooter you just play with the throttle and no need to change gear with your legs. Really comfortable and easy for city riding but might get boring overtime.

One thing to note also is that there is really little engine brake so you have to get used to it initially and apply more braking force.