VO2Max is a complex combination of the body's ability to take in, absorb, transport and utilize O2. While I believe both the intervals and the ride would have benefits to the body I also believe those benefits would be different.
For VO2Max, my bet would be on the intervals -- especially depending on how you do them (and specifically their intensity and duration) because the intervals have the ability to systematically and predictably stress all of the systems and processes that are part of the VO2Max equation.
Conversely, I would also suspect that 2 minute intervals may be barely enough to stress all of those systems -- by the time you get all the systems running at their (near) maximum capacity, you shut them down.
My exercise physiologist has recommended 4 minute intervals for me alternating between 80-82% MaxHR and 95-97% MaxHR. In actuality, I divide the 'rest' period into 2 minute halves: 2 minutes bringing my heart rate down and resting; then 2 minutes (or 1.5 minutes) bringing it back up to 95% -- so my actual interval is actually more than 4 minutes. Actually, my 4 minute high intensity interval starts where yours ends.
... I do 3 sets of them bracketed by a 4 minute 90% interval bookmarked at each end.
During that 4+ minutes ALL of my systems are being stressed to their near maximum capacity and thus building on my overall VO2Max.
Well, that's the theory anyway!
... I'm sure I'll get some push back from those doing 30 second intervals.
....... But, when you change the equation, you change the results.