When evaluating the quality of armor, not all stats are of equal importance. Some classes prefer certain stats and don't care about the rest (e.g. Hunters may want to ignore Strength but care greatly about Mobility). In the Settings page (or in the Organizer) you can configure a "Custom Stat Total" separately for each class and use that total all over the app. It shows up in the item popup, Compare, Organizer, and in Item Search. For example, searching stat:custom:>30 can help highlight items where the selected stats total up to a certain value.
In Settings, click on the icon for each stat you want to include in your custom stat. This configuration is saved per-class, so you will have a different custom stat for Hunter, Titan, and Warlock gear.