Answers will vary, but here is my point of view:
First used Persil (normal powder formula with oxygen bleach) with my first front loader (Malber), and didn't see much difference between it and other low sudsing/HE detergents such as Wisk tablets, or other detergents such as Tide or Cheer Free powder with some grates soap added to kill suds. However now that the Miele W1070 is my daily driver can say there honestly is a difference. Persil really does shine well using the traditional washing programs of "Euro" front loaders with their heated and long cycles. Everything comes out clean, white and bright without additives when I use Persil, and more importantly rinses are cleaner. In fact by the third rinse (out of five)the water is totally clear and interim spins are faster and "easier" on the machine since it does not have to force out all the froth which comes from normal detergents.
IIRC Henkel Persil formulas do not contain phosphates, but do have phosphonates.
Mega-perls are the concentrated versions of Persil powders. IIRC Miele USA has been phasing out importing Persil powders in favour of the perls.
Your results with Persil will vary, and the only way to find out is to try some out for yourself.
L.