With regards to who is better to work for, I would say it depends very much on your personal circumstances.
Ryanair will offer you permanent employment with a pension contribution and a fixed 5-4 roster with no scheduled overnights. If you live near a Ryanair base and you're lucky enough to be based at home, your quality of life increases enormously, however basing seems to be a little bit of a lottery with no guarantees and no seniority list to govern who goes where and when. Alternatively, I believe the option to work as a self employed contractor through McGinley is still available and there is plenty of info about this arrangement on here. Time to upgrade if you join meeting the requirements can be as little as 6 months, but the downside is that you will most likely have to move base upon completion and the base lottery starts all over again. You will have to cover all job related expenses, i.e. uniforms, license, medicals, transport, hotels and there is no crew food.
Norwegian is a different kettle of fish. You will be offered permanent employment, however it is permanent employment with an agency that is partially owned by Norwegian and salary, pension contributions etc are currently being negotiated with local unions. There aren't as many bases to choose from and Scandinavia is off limits for now, so you're looking at Helsinki, Rome, various Spanish bases and Gatwick. The company is heavily unionised and base allocation is based strictly on the Master Seniority List, so it may take a while to get your base of choice. The operation includes a fair amount of overnights and the roster is variable, published 1 month in advance and includes 12 days off per month. As far as command is concerned, expect at least 2 years and there is a tough evaluation process to get through before being accepted on a course. You have the option to go to long haul on the 787 if you wish, internal applicants get preferential treatment. All job related expenses are reimbursed, uniform and crew meals are provided. Job stability is less than at Ryanair, with redundancies having occurred in the winter for the last 2 years.
The differences in pay between the 2 companies are negligeable, it's much of a muchness, with Ryanair offering a slightly better deal as far as I know.