I do not know if Diamond uses lesser quality meat or not. If what you say is true it turns out to be six of one & half-dozen of another since Purina uses corn & other grains to keep their costs down.
You say you'd rather have less high grade meat than more low grade meat. Firstly, I do not think you can be sure the meat used in Diamond or Black Gold is of lesser quality than that used in PPP. Secondly, a dog fed a corn based feed is still on the short end of the stick even if the meat in other feeds were of lesser quality, b/c a dog's system can't use corn & the allegedly higher-quality meat they do get is in such small amounts it's a non-issue. What is better for a dog? Meat or corn? A dog will eat rotten meat (& get more from it) before they will corn.
If you want more calories in a food, try Diamond Hi-Energy or Black Gold Super Blend. Or you could just try putting a few Dollar Store sardines in their food!
But seriously, if you are happy w/ PPP, by all means continue using it. In the end the only opinon that should matter to you is yours. My point was that a fancier can find a better feed for their money, to include products manufactured by Diamond or Black Gold. Plus, by foregoing Purina products you also won't be supporting a company that is purposefully misleading unsuspecting customers! While I think about it, Purina Co. is probably price gouging too since most of the ingredients in their dog foods are not that expensive! ($17 for 20lbs??? Yikes!)
But here is a examination & summary of PPP. See what is says. I'm sure you will find it interesting. Here it is:
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EXAMPLE 2: Ingredient list for ‘Purina Pro Plan’ adult lamb and rice formula:
Lamb, brewers rice, corn gluten meal, whole grain wheat, chicken meal, beef tallow preserved with mixed-tocopherols (source of Vitamin E), oat meal, pearled barley, fish meal, dried beet pulp, natural flavors, dicalcium phosphate, calcium carbonate, potassium chloride, salt, L-Lysine monohydrochloride, choline chloride, vitamin supplements (E, A, B-12, D-3), zinc sulfate, ascorbic acid (source of Vitamin C), ferrous sulfate, riboflavin supplement, niacin, calcium pantothenate, manganese sulfate, biotin, thiamine mononitrate, folic acid, copper sulfate, pyridoxine hydrochloride, menadione sodium bisulfite complex (source of Vitamin K activity), calcium iodate, sodium selenite. H-4470
Analysis - our opinion
Top 5 ingredients - Lamb, brewers rice, corn gluten meal, whole grain wheat, chicken meal
Comment - Two named meat sources in the top five ingredients, but we note that the first is lamb (inclusive of its water content) and the chicken is the fifth ingredient. We are not confident that the total meat content of this food is high compared to the grains. We prefer not to see brewers rice (by product of alcohol industry), corn gluten meal or wheat in a dog food.
Other ingredients - Beef tallow preserved with mixed-tocopherols (source of Vitamin E), oat meal, pearled barley, fish meal, dried beet pulp
Comment - Beef tallow is a low quality animal fat which we prefer not to see in pet food. Oat meal and barley are fine (barley is a whole grain) but we are not so happy to see beet pulp included. Fish meal is another meat protein source, but is likely to be preserved with ethoxyquin. Food contains no whole fruits or vegetables.
The rest - Natural flavors, dicalcium phosphate, calcium carbonate, potassium chloride, salt, L-Lysine monohydrochloride, choline chloride, vitamin supplements (E, A, B-12, D-3), zinc sulfate, ascorbic acid (source of Vitamin C), ferrous sulfate, riboflavin supplement, niacin, calcium pantothenate, manganese sulfate, biotin, thiamine mononitrate, folic acid, copper sulfate, pyridoxine hydrochloride, menadione sodium bisulfite complex (source of Vitamin K activity), calcium iodate, sodium selenite. H-4470
Comment - We prefer not to see artificial flavours and colours added to dog food (“natural flavours”) or the use of salt.
Preservatives - Mixed tocopherols
Comment - Uses naturally-occurring preservatives
Conclusion - Not a food we would choose. We note that the top five ingredients do contain 2 named meat protein sources, but since the first ingredient is ‘lamb’ inclusive of its water content and the second meat ingredient doesn’t occur until 5th on the ingredient list, we are not convinced that this food contains a reasonable proportion of meat protein versus grains. (This is what makes PPP a corn based food despite it's intentionally misleading MEAT AS THE 1ST INGREDIENT claims - MSU Dawg)
There are no whole fruits and vegetables in this food, and note that the grains used are ones we prefer to avoid (corn gluten meal, brewers rice and wheat) and which are common allergens. We would not buy a dog food with corn or wheat in the top five ingredients, and prefer not to see these grains at all.
We do not like to see artificial flavours or colours added to dog food, nor the use of salt.
Naturally occurring preservatives are used in this food.
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"But because of his great love for us, God, who is rich in mercy made us alive with Christ even when we were dead in transgressions - it is by grace you have been saved." - Ephesians 2:4-5
I feed him Eukanuba Lamb & Rice which is made for more inactive dogs and has about 386 kcals per cup, or I feed him Euk Adult in the winter which has 405 kcals per cup. Euk also only has chicken or lamb instead of chicken or lamb meal as the first ingredient, but its a good quality food with a good vitamin/mineral list, high kcals and has not failed me in the 5 years I've been feeding it.