Is the Android Galaxy 6's rate of battery usage more steeply affected by each additional application added to the phone, compared with the amount that an additional app would increase the battery usage rate on other types of phones, like the iPhone or the Windows phone? I ask because I just upgraded to an Android Galaxy 6 after years with one of the oldest Windows phones, and despite the many inconveniences I happily bid farewell along with the Windows phone, the battery life on the Galaxy, with no extraneous(by that I mean other than basic call, text, and voice-mail functions) apps other than yahoo email syncing, is TERRIBLE compared with that of the Windows phone with several more "extraneous": apps, even at that phones oldest. Hopefully some of you can speak empirically to this..?
Having more apps installed to your device storage will not at all affect your battery life, unless perhaps your storage is nearly full and the OS / storage controller needs to spend extra time finding free blocks.
Running more apps will certainly affect your battery life. Many apps will use services, or register broadcast receivers that get events and run a task, etc. thus using CPU time and battery. However, this is absolutely not different from other mobile OSes.