My 2c...I disagree (slightly) with Ivan. Who is to separate you or anyone from the phone they want? I'd say figure out what you want in a phone (iOS vs Android, specs, features, customizability, ease and cost to unlock and/or accessorize, how important the brand is, etc.), then make a wishlist (say I want phone A, if I can't get phone A I'll settle for phone B, else I'll go with phone C). Then go for the best deal. Best deal will factor in the total monthly plan, upfront incentives, and the buy-out. Other factors are the inevitably obvious (does the carrier cover the locations where you use your phone).
As I am a big Motorola fan, I keep coming to Koodo for more Motorola's. Koodo has awesome promos on Motos and I just can't get enough of 'em.
Of course, it works out cheaper for you, and you actually want the OnePlus, Asus Zenfone, Xiaomi, etc., or just don't care what handset you want, and over 24 months it'll be cheaper to buy a phone outright, then go on a BYOD plan, then do that.
@Brian: since you switched one of your phones to Virgin, that's a Bell subsidiary, and Koodo is a Telus subsidiary, basically, you're connecting to the same cell towers whether on Virgin or Koodo.
Having one line with Virgin is not a bad idea if you actually benefit from their member benefits. I've used their member benefits only once for a small discount on airfare. Didn't come anywhere close to the credits I got from Koodo through their refer a friend program.
Virgin Mobile also has a decent phone selection, but doesn't have as good a selection on Motorola's as Koodo has. If you don't care about Motorola's, phone selection between Koodo and Virgin should be *mostly* trivial (perhaps a bit better on Virgin as they won't have online-only phones, plus they're competing with Fido right now on a trade-in deal on the LG G6).
Virgin Mobile gives the same gift cards on upgrades as new activations at 3rd party kiosks such as The Mobile Shop, Best Buy and Walmart, making Virgin Mobile an appealing choice for those who upgrade frequently.