I would like to discuss filing a PCT as a first application.

As I understand, the disadvantages are:
The higher payment at the beginning of the process (paying the fees a year earlier).
Having no application on queue for examination.

As I understand, the advantages are:
Getting the written opinion earlier (if it is positive).
Having the opportunity of using more patent prosecution highways

Can you add arguments to this short list?

A further question - to what extent can a PCT application be amended, and does it depend on filing it as a first application?

Thank you,
Ophir.