1

I think Amman is the better choice for you. Are you planning to just stay put and do day trips from one place?

With Amman you are far likely to meet up with other solo travellers, if you stay in one of the recommended travellers hostels/hotels, thqn in Muscat. As I remember, there are day trips on offer anyway, so you probably don't even need to find someone to share costs with. Some I can think of off the top of my head would be -
Madaba, Mt Nebo
Dead Sea
Jerash
Or if a little more adventurous, you may even sign on to an overnight tour down to Petra
All this can be done also by public transport as well but if, as you seem, a little nervous then take the hotel organised tours.

Muscat also makes sense as it's a short flight, nice enough city, no tourism hustle bustle. Drawbacks are cost of hotels and if you are wanting to go out of Muscat, only very expensive guided tours. Though, there is an easy bus route to take you to Nizwa, which is excellent for a couple of nights. 2 hours trip and quite a few sights in the town and nearby area.

Read up more on the possible things to see and decide what interests you the most.
Amman will offer more of a contrast with Dubai for you, than Muscat. More exotic, more colourful, more noise.

2

I second jennifer views.Amman is more suited for your purpose of visit.There is a dozen a so hotels and hostels in down town Amman they offer tours to their guests.
If you decide to go to Muscat i would prefer to travel by road than fly.

3

Thank you both so much. I think we have a winner....