Having just done one of each to my recipe recently I’d say split pea actually has more body and inherent flavour.
Main difference is split peas really do need simmering for an hour where red-lentils are done in 20 minutes. And split peas are cheaper than red lentils, though a 5kg bag of red lentils (which local supermarkets do not stock as they prefer to sell you 1kg for double the price or 500g for quadruple the price) is not a bad price.
Ideally you do a dhal with red lentils, boiled in one pan or added at 20 minutes remaining to the pan of green lentils, yellow and green split peas boiling for an hour. Soaking the peas and green lentils overnight may help.
The reason to mix all of them is what is called “protein-complementing” each pulse/legume has it’s own amino-acid profile and mix them together and you get what is called “complete-protein”.
anyway, a suggestion to feed 4 -6:
half cup green split peas – simmer 60 mins
half cup yellow split peas – simmer 60 mins
3/4 cup red lentils – simmer 20 mins
1/4 cup green lentils – simmer 30-40 mins
Add a banana to the boil if you like banana, sweetens it up nicely. and 4 or 5 cardamon pods and 1tsp turmeric.
I use double the cups of water to pulses, so 2 cups pulses, 4 cups water, but keep an eye on it add more water if required.
then once that has all been reduced to a nice mush, fry up one or two onions to soften them, and make up your curry spices into a paste and then fry it,
my spice mix is :
1tsp cumin. 1tsp ginger, 2tsp coriander, 1tsp turmeric, 1tsp fenugreek/methi, 1 or 2 tsp hot chilli powder (depending on how hot you want it, 1 is quite hot), 1 dissolved veg stock cube, mix that all up into a paste and then fry that with the onions, then pour in the pulse mush and simmer for 10 mins or so.
serve with any combination of spuds, rice, bread, pitta or nan.
Water it down a bit for a spicy soup.