I sailed on the Ocean Nova with Antarctica21 in 2018, on their first trip of the season. Full disclosure: this was my first and only cruise, so I have no comparisons with anything else.
Let's be blunt: the Ocean Nova is very basic in terms of amenities, but it had everything you need. Beds were clean and comfy enough with daily housekeeping, 3 nice meals per day (buffet breakfast and lunch, multi-course plated dinner), and even laundry services (extra charge). The small ship size probably made the Drake Crossing rougher, but it meant there were 67 passengers total, so we easily made 2 landings per day. That makes it a great mode of transport to get to and from your destination. However, if you're someone that relishes in "the journey" and wants your Antarctic adventure to look like traditional big-ship cruise experience, it won't not the best choice.