IMO a smaller phone + tablet is better than carrying a phablet. Why not get the iPhone 6 to replace the 5s and 5 then get a cheap phone as your secondary phone. That way, when one of your devices runs out of power, you still have another to use (either the iPhone or the iPad).

I don't usually bring my bag when I go out and I always put my phone in my pocket which is why I stay away from phones with 5 inch+ screens