Note that SU has a subscription option that will install to your local machine.
The SU Pro (subscription) version does come with a few extras, but consider if you really need / use the (additional) functionality, running the risk of being locked out of your work if you choose not to renew your subscription licence. Sure, technically you could open SU files with the free version if you’re locked out, but if the files is commercial product, then the free licence prohibits you from opening those, let alone do any other work to them.
Get the SU Pro Classic (perpetual) licence, there’s no looking back. Even with the optional annual “maintenance and support” of (currently) $120 p/a from year 2 onwards, after a few years this becomes more cost effective than subscription licence.