HT, if I may reply. We just did that exact thing you suggest. We arrived 14:30 and stayed in the Vision Hotel, which is quite good indeed. Arranged for evening cruise but too bushed from the flight. You will likely be even more flagged. The rendezvous with the first bus was only 8 minute walk dragging our roll-ons. But you have to meet them at exactly the time they say. Bus cannot wait. Call Viking and get boat and program director's number and they will set up and text when they leave Komarom.
I will say the trip has been remarkably rewarding. Shore tours are excellent, and the organizational coordination is top notch in every aspect. This river cruising is industrial tourism, with 5 or 6 30-person groups from each ship, some following the same overall path but spaced so we don't trip over each other. With some 10-15 ships at same location, so multiply the crowd at the popular spots accordingly. Weather has been chilly but pretty sunny.
The cruising on the ship is an experience of perfect appointments and service. You will enjoy it. But by all means recover in Budapest. Even though you miss out on the excellent food and accommodations you would get on that last 1.5 bus ride.