One-time purchase is a billing option for purchasing VDIT Pro lifetime without any further additional charges. You can enjoy life-long access to VDIT Pro after a one-time payment.
Subscription is another billing option for use with VDIT Pro. Depending on the billing cycle you choose, you pay your bill monthly or yearly. With this subscription, you can enjoy the VDIT Pro at a lower cost than if having chosen one-time purchase.
However, since the billing will be made as per the cycle chosen, if you do not wish to maintain your subscription, then you must cancel it. You can cancel the subscription at anytime. Please check How do I cancel my subscription? for details.
Both billing options, one-time purchase and subscription, will grant access to the same VDIT Pro with all the same Pro features.
Please download VDIT to explore more various features!