The Yellowfin 17 Skiff 2012 is a modified-V design and the Yellowfin 42 2012 is a deep-V design, so you're likely deciding between two noticeably different on-water experiences. Hull type shapes everything from ride quality and fuel burn to dock handling and resale trajectory.
The power gap is worth calling out. Rated to 1 400 hp, the Yellowfin 42 2012 has a 1 285-hp advantage over the Yellowfin 17 Skiff 2012's 115-hp ceiling - enough to notice on acceleration and at cruising speed, particularly with a full passenger load. Fuel capacity breaks the other way: the Yellowfin 42 2012 carries 600 gallons versus 18 gallons in the Yellowfin 17 Skiff 2012. On a lake day that's negligible, but for coastal cruising or long reservoir runs the extra range matters.
For family outings this is probably the sharpest distinction between the two. The Yellowfin 42 2012 is rated for 12 passengers, while the Yellowfin 17 Skiff 2012 caps at 5. If you're regularly pulling extended family or a group of friends onto the water, the extra seats on the Yellowfin 42 2012 could be the deciding factor.
Bottom line: Choose the Yellowfin 42 2012 if your priority is putting more people on the water - it handles 12 passengers and at 42,0 ft it has the deck room to back that rating up comfortably. The Yellowfin 17 Skiff 2012 is the smarter pick if you want a lighter, easier-to-trailer boat rated for 5 that costs less to run day-to-day.