Opinion:
As you said, sphera is better. How much better? I can't tell for sure.
After diving daily with the sphera for over a week, I was using a minima once again. After ascending up from about 26m~ (the bells in dahab. ) I felt like there was a cloud of bubbles engulfing my head (I don't tend to sniff the mask air back).
I can't quatify the amount, but it felt like a lot more.
The narrowed filed of vision was also noticable.
I remember Bevan once did an experiment and took the sphera and the minima down a line the deepest he felt possible without equalizing them. I don't remmeber the results (both around 10m), but the sphera got a few meters deeper. If you still have both the masks, it's an easy experiment.
As you said, sphera is better. How much better? I can't tell for sure.
After diving daily with the sphera for over a week, I was using a minima once again. After ascending up from about 26m~ (the bells in dahab.
I can't quatify the amount, but it felt like a lot more.
The narrowed filed of vision was also noticable.
I remember Bevan once did an experiment and took the sphera and the minima down a line the deepest he felt possible without equalizing them. I don't remmeber the results (both around 10m), but the sphera got a few meters deeper. If you still have both the masks, it's an easy experiment.