if you can get the spec cheet for the MBZ filter for the WIX and they maych up for rated flow, pressures, and efficiency (usually a beta ratio) and the WIX looks comprable, I would have no problems using WIX or any other brand if the build quality looked good. luckily with these canister type filters build quality is much easier to determine. if you doubt anything, cut the OEM and other one open and look. some manufacturers have a nasty habit of giving you a cross reference filter that fits the hole, but isn't up to spec.
Finally, a voice of reason. I became a fan of Wix over a little Mazda B2200 commuter vehicle. Mazda changed the specification on oil filters requiring TWO anti-drainback valves vice one. Fram and all of the other filter manufacturers/sellers adhered to the "old" specification instead of updating their product. Wix changed theirs.
The shop where I take my 420 SEL couldn't even give me a good reason aside from their M-B parts suppliers give them better discounts on Mann filters over other brands.