Should I use urethane spray foam or foam rope for caulking wide gaps?
There are pros and cons to each, making this a subjective question. Here are some comparison points. 


Rope caulk is easy to work with. You can take your time and not worry about anything curing too soon. Urethane is potentially disastrous, as it bonds very well to almost anything it touches. Permanently. It cures in a few minutes or slightly longer, depending on environment.
Urethane seals better due to the bond it creates. Rope caulk also seals well, but in cases where size isn't quite right you may have gaps. 
Urethane fits a wider range of gaps. You can easily fill narrow slits to voids several inches or more wide. Rope caulk comes in various sizes, but there are often compromises during installation. 
Rope caulk is cheap, and you can use it now and later. Urethane foam isn't much more expensive, but you have to use the can in a fairly short time since the nozzle will seal itself shut. 
Rope caulk can be removed for repositioning, changes, etc. Urethane would need to be cut and scraped away, usually leaving a residue. 


Silicone and other topping caulks would need to be tooled to overlay backer in wide gaps. A combination of putty knives and other items can come in handy, along with a finger.