We paid cash for both during trips last year. I’m a Poly person to the core (and I like WL too)… but for us the Cabins won out as a more enjoyable experience. No doubt both are awesome in their own way, but if I had to pick one it would be the Cabins.
I think the layout of the cabins, the screened in porch, the hot tub vs. dinky splash pool, and overall setup of the Cabins within WL is a better product than the Bungalows. Parking and access is more convenient too. They are just super cozy and livable, IMO.
The Bungalows are more “Disney” though as the vibe of the Seven Seas Lagoon is unmatched. If your Disney newbies are really into seeing the MK, fireworks, Electrical Water Pageant, etc… then the Bungalows should get serious consideration. Perhaps a bit more of a ‘wow’ factor for sure.
They had a soft goods refurb earlier this year (after our stay last year), but our Bungalow was frankly a bit dinged up at the time (big scratches on the kitchen table, wood floors, etc). The Cabins are a little newer/fresher.
If this is during a hot time of year, the walk through the Poly grounds and out to the Bungalows can be a little surface of the sun like - if that’s a concern for you. The cabins require outdoor access too of course, but to me they feel closer and the various paths have more areas of shade.
This wouldn’t impact which one I’d choose and is more just a whiny personal beef….but as a fan of both resorts I’ve always been really impressed with how Imagineering incorporated the cabins into the WL grounds in a manner that looks like they’ve been there for decades. They seamlessly fit in and took effectively nothing away from the resort.
To me, the Bungalows feel like a mis-matched added appendage to Poly. They took away a lot of great view/sight lines and don’t even really fit in with the look of the rest of the resort. It’s not outrage/fatal flaw level for me, I’ve just never really loved the look. Plus the sound of the pump occasionally kicking in to suck wastewater away isn’t all that luxurious.

Sorry, rant over.