As Chelle mentioned there are a lot of opinions out on home cooked, for that reason I think research would be your best bet. Hit the books and find some details that will equip you to learn the benefits of both options. Once equiped with information you can analyze and decide.
One book that is pretty popular, and therefore pretty easy to get ahold of (often you can even find it used in larger book stores that carry used books, Powells Bookstore for example), is Dr Pitcairn's Complete Guide to Natural Health for Dogs & Cats. I'm not saying it's the only reference you need or the best, simply that it's got some good information and that it's one of the easier books to find. It's a good starting ground... 
Personally, I am not a fan of canned food - due to the plaque that type of diet encourages. You mentioned in your reply about a little dog, having been around numerous chihuahuas in my family I can tell you that a canned diet requires a lot more dental maintenance (cleanings). Poor dental hygiene can cause other health issues.
If you want a commercial food that has been researched to have the nutrients for your dogs then my suggestion is look to the high quality kibbles. The Whole Dog Journal puts out a list of the top 10 and is a great resource for this type of research.
If you don't think your dogs are exhibiting the overall health they should then, yes, I too would look at the diet as a possible cause.
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tabitha
Kayo, Kahla, and Dante'
