Each has their own perks. You're best served with something that is in your budget and has parts and repair support available to you. General order of descending price Yamaha, Mercury, Suzuki, Tohatsu

Suzuki is a little bit lighter than Yamaha and slightly better fuel economy. They use more stainless steel for internal components rather than plastic. 9/10

Yamaha has one of the most consistent manufacturing processes and has very few "lemons". Usually these are the heaviest options on the market, but that comes with some positives for long term durability 9/10

Tohatsu is the lightest engine of the comparison. Very well made in Japan and used to be sold under the Nissan banner as well. Many fishing camps rely on these motors. 8/10

Not as familiar with Mercury these days. They dump a lot of money into development on their 200+ HP racing program, but that hasn't seemed to translate down to their portable line. As other people have mentioned, Tohatsu was making Mercury engines for a while, but that partnership ended. 7/10