I think that they would be more directly compared to a hydor or tunze than a vortech - due to their style. I don't have have any Tunze to compare it too but they are an upgrade from the koralia's for sure. I am running 4 mp-40's and one thing that I don't like about them is the inability to direct the flow, sometimes it is just a lot more convenient to be able to! Obviously, the wp-40 has a bigger in-tank footprint than the vortech, as well as having the cord in the tank - and because of it's style is definitely quieter. The flow reaches farther across the tank for sure than the vortech, it moves a ton of water. It does not have all of the fully adjustable modes that the vortech does but has enough in my opinion..... but then I rarely use more than the nutrient transport mode with my vortech's anyway. I can't tolerate the noise from reef crest and don't feel the need to change between modes. Adding one to my 300 made a very noticeable difference in the flow throughout the tank ..... and this was all the way throughout the tank from top to bottom so even if it doesn't supposedly have the "undertow" that the vortech's have, it certainly increased water movement thru the entire tank.
Will they replace vortech's? I think that depends upon what each person wants ..... do you mind the bigger in tank footprint and cord in the tank ..... and of course how well they last. Personally, I do like my vortech's but if I were to set up another tank right now I would definitely try just using the wp-40's and/or 25's soon to come out if it were a smaller tank. I think that one of them does more than one vortech ..... and you can darn near get 4 for the price of one. So, for me, assuming they do hold up, I would be happy to deal with the cord and footprint for the silence and price ..... and just as good of flow results.