Tri metal will absorb abuse and contaminants easier-embedability is better than with Aluminum. Aluminum is better to run with tight clearances and thinner oil, they've been widely used in newer engines for at least 20 years now. Cost, I think, is kind of a wash depending on the app. Aluminum, when used properly and with good clean oil, actually kinda polishes the crank journals, but for most older designed engines, the tri-metals are probably the best/safest/most reliable choice.