Unilever Persil
I've been finding that Unilever Persil also out performs Ariel in many ways. Much of the Ariel "fresh clean" effect seems to rely on leaving a very pungent smell on the fabric. Even after 4 or 5 rinses, you can still smell it really strongly on your clothes.
I find Persil cleans just as well, if not better, particularly on oil splashes (e.g. salad dressing). Persil has removed those on a very short 30C wash, while Ariel has left traces.
The clothes come out smelling clean and not heavily perfumed. It does have a slight fragrance, but it's nothing like the smell of Ariel! If you leave a box of that stuff in a room you can smell it when you walk in, and that's without even opening it!! It's not a floral scent like what has been described for South American products, rather it's a kind of citrus/pine or slightly herbal aroma. It's very distinctively Ariel. It's not unpleasant and it does smell "clean" but I just think it's very unnecessary.
Persil's smell is not floral either and is quite subtle. It's closer to the scent you'd get in a shower gel or a shampoo and it doesn't really linger on the clothes strongly.
Their S&M liquids smell very like a non-floral shower gel / shampoo. Slightly citrus / herbal. I would rate them as having the best scent of any of the detergents on the market here. It's fresh and pleasant but not overpowering.
Older Ariel formulations were not as heavily perfumed, yet had a distinctive scent which I actually liked. The new formulation scent is just not my cup of tea at all.
As for rinsing :
Persil - after one rinse + interim spin on the second rinse the water runs clear.
Ariel takes at least 3 rinses and interim spins for that result.
Foaming:
Ariel - foams quite a bit
Persil - you'll see little/no foam during the wash.
Cleaning:
Both provide excellent results.
Persil performs better on oil/grease/makeup/cosmetic marks.
Also, I tend to use non-bleaching detergents i.e. colour forumulations more than 'universal' formulations.
Persil Colour definitely performs better.
Ariel Colour and Style is, in my experience, second best.
Also, possibly because it rinses so well, Persil seems to leave clothes much softer. E.g. if I tumble dry towels after washing in Persil Powder they come out very fluffy where as if I do the same with Ariel they're definitely a little 'stiffer'.
Also, Ariel Colour smells quite different to the normal version of Ariel with oxygen bleach. The Colour version's smell is a lot more acceptable in my opinion. I find the normal version a bit too overpowering.