We drove from Sierpa to to Drake Bay in under three hours complete with photo stops after crossing on the small car ferry in Sierpa. The road is steep, curvy and rough at points. We only used the 4x4 to cross the river 4 kms outside of Drake Bay and that was a precautionary, rather than necessary measure. Our rented Bego was about smallest and most basic 4x4 available in CR. We drove back to San Jose via Chacarita, the coastal highway and San Isidro over the space of a few days with a road time of 7 to 8 hours. The vehicle had a manual transmission and with this, was adequately powered. The clearance and suspension was more than a match for the road conditions we encountered. Range on 50 liters of fuel was 500 kms regardless of driving conditions.
You can park in Sierpa and take the boat ride and see some interesting things, but you will miss the spectacular views afforded travelers on the Sierpa Rincon road as well as the adventure. You will also see some of this on boat tours out of Drake Bay. Driving by road also lets you see more of how locals manage and understand a little of what is behind the Pura Vida tourist curtain.