I use my Priv as my work oriented phone and my SE as my burner/personal phone. I move back and forth throughout the day. Here's my take...
Priv is good for work because the Hub handles email the way I like. It has a fil may stem so working with attachments is easy. It simulates Push email even with non push accounts. It also has the physical keyboard so if going on a rant I can type really fast. Best feature is the predictive keyboard, which is sadly inferior on the SE even after months of training. Priv accels in email, messaging, attaching, and anything storage related, like OneDrive integration. It's a large device. Battery usually lasts all day and only requires me to recharge each night. Notifications are well designed and needed for my work situation. Visible LED, louder volume for notifications than media, flexible alarms are all needed items.
SE is fun! Really great form factor, simple to grab and open with Touch ID, and Apple Pay beats Android Pay by a lot. Hey Siri is much better then Hello Google... I often joke around calling one out vs the other to see which gives a better weather report. The SE display is better in sun. The SE is naturally waterproof so better for a beach day. Camera is fast and takes a great picture, and features like photo stream and handoff make it useful for home activities. The interface to my iMac with messages is ideal for after hours texting with friends while still "working" at the computer. Up until Marshmallow I liked the fine grain controls of iOS in certain instances but I'd say that is equalized now. iTunes for loading and removing content is manageable and in some cases preferred, I've lost things on the Priv not because no careful. The office apps are usable on the fly and this is bolstered by how iOS has the edit bubble which is superior to android text editing.
Each has its own niche in my life. I rarely feel like swapping. To keep continuity, I use an SMS app on the April which lets me forward texts to any phone. That way I can keep track of both worlds when I grab the SE for a hike or swim.
Typed on my iPad, so all errors are crappy predictive text induced, and I take zero responsibility.