Honestly, each requires such different care that I can't call any easier than the other. For instance, my rats, hams, gerbils, and guinea pigs all required cages with appropriate bar size (which was a trick with the rats--boogers are smart!) and space as well as constant upkeep: I fed oxbow which isn't cheap, and they lived on fleece, eco-bedding, and carefresh with bi-weekly cleanings due to my own health issues. I ended up doing meds on all of them toward the end of their lives, either for infections, pain, or vitamin deficiencies.
The cats have always had health problems, be they the family cats or my own: my mom has had cats on prescription foods/medication all of my life. I have a blind bottlebaby who needs daily meds at the age of 3 for several problems including nerve pain in her tail, infections in her remaining eye, and herpes. Her "healthy" brother is on prozac.
My best friend has reptiles and their care is just as tedious as the fish--there needs to be certain temps, lighting, substrates, etc, and her snake only just finally started taking meals with regularity. He's 4.
And working at a vet clinic, I have to admit that I've seen so many dogs with diabetes, thyroid problems, and allergies... It really just comes down to what you feel is easy--walking a dog vs cleaning a cat box, cleaning a cage vs doing a WC on your tank. That kind of stuff.