My beloved vintage crock pot just kicked the bucket (in the middle of me trying to make some bone broth). I need to buy a new one ASAP! What's the best of the newfangled slow cookers out there? I'd prefer one that could fit a whole chicken.
The 3 things I like best about mine are: oval shape to accommodate whole birds or roasts (as you mentioned), ceramic insert which is fairly standard these days and "manual" controls that don't second-guess me. It stays on whatever setting I select until I change it. The lack of timed cycles actually makes it cheaper which is a plus. I paid less than $30 for a 7-qt cooker because it isn't digital.
Honestly, I think a crockpot is a crockpot. We've had my little sister's cheapo cast off for years and although it's a little small, it does the job perfectly well. There's very little with them to go wrong. Aside from looking snazzy on your worktop, I would go for the cheapest one available in the size you want and spend the extra money on good quality meat to put in it!
Vintage crockpots are the best in my experience (I have 5, don't ask...). I find good ones at yard sales and thrift stores. 80's and earlier (Rival or other brands) are better - the new ones tend to run hot. I do have one newer one that I like made by West Bend. The newer Rivals run way too hot.
Any large dummy slow cooker or rice cooker that has no extra fuzzy logics etc. Then add an pid controller to that. That way you can precisely sellect the cooking temperature. PID controller will hold it within 0.5F degrees. Great for many things.