One of the main difference is on the need to apply for consent to transfer and consent to charge when you are buying a leasehold property. Hence, the usual 3+1 period to complete purchase of properties that requires consent will only start upon getting the letter of consent to transfer from the Land Office as shown here.
Another important distinction between freehold and leasehold is on the need to renew the leasehold's tenure (99/60/30 years) which requires the renewal premium.