I've flown Porter a few times this year and they're pretty cool. If you can get a seat sale I recommend Porter as the prices are then pretty decent otherwise it can be a bit expensive.
The planes are tiny and feel like they fly differently from other planes and landing at Billy Bishop is always a treat but I won't confuse the airport with Porter Airlines.
I've only ever flown Porter short distances so there really isn't any service minus a drink and a snack but they crew are always friendly. On short flights there is a possibility that your carry on might not be able to go with you so unpack what you want on your flight in case you have to leave your bags at the door.