I would recommend 5-point for safety. When shoulder harnesses on a 4-point are cinched tight, the lap belt is raised up off the hip bones (onto the belly). If you wreck, the lap belts will dig into the belly and can cause internal organ damage. This is the same type of injury caused when children do not use a booster seat in a car. When the lap belt is properly positioned on the hip bones, there is little chance of internal organ injury.
5-point harnesses have a sub-belt (crotch strap) added, which keeps the lap belt positioned proerly when the shioulder belts are cinched tight.
For convenience, I recommend spending a few extra dollars and buying belts with a Cam-Lock latch mechanism. I spent years fumbling with Latck-Link belts in race cars. We had to replace the belts every two years and I didn't care to spend the extra money on Cam-Lock belts every two years. One time I was out of stock on Latch-Link belts and had to pull a set of Cam-Locks to make a race. They are so much nicer, that I'd never go back to Latch-Link belts!
Cam-Lock belts have a receiver , into which the other four belts are simply plugged-in (just like seat belts in your car). There is no sequence that needs to be followed when buckling up, just grab a belt and click.
Latch-Link belts must have the links of four belts assembled in order, then the latch must be opened with one hand while the assembled four pieces are installed into the latch assembly. Finally, the latch must be manually closed. As you can see, assembling the Latch-Link is not easy or simple, and it's even harder when wearing gloves.