6061-T6 is the workhorse: good strength, excellent corrosion resistance, weld-friendly, and widely available. It machines predictably and anodizes well for consumer and industrial housings.
7075 offers higher strength and is common in weight-sensitive structural brackets, but it is less corrosion-resistant without protection and is generally less weld-friendly than 6061.
Choose based on load case, environment, joining method, and finish. If you need both strength and corrosion, consider whether a protective coating or a stainless option might be more reliable than pushing 7075 without a plan.
Always specify temper (T6, T651, etc.) and any directional grain concerns for plate applications.