I will give you info only on the two to help your decision. It based on experiance, and info I have gained. I was going to respond to a thread on stage 1 vs powermax but there is so much info I thought just start a new one to get the info out.
Now before I have a bunch of powermax owners taking shots at me, remember one thing, I have numbers to prove all I say and have built over 250 turbos and counting, I know a lot about the 6.0 powerstroke turbos, not all but probability more than any other members on here, just due to how many I have played with. I have also know why the powermax performs the way it does. I'm more than happy to help anyone one out and will answer questions anyone may have about turbos.
First of all I don't like to build the MTW stage 1 turbos with a 03 (10 blade wheel). The MTW stage 1 turbo, is 850.00 with the billet wheel + 450.00 for refundable core charge. The turbine wheel is a 13 blade wheel, for quicker spooling, and throttle response.
So what is the advantage of the MTW stage 1 over the out of the box powermax:
First tuning is easier, and spool is faster, flows more air, so makes more power.Spool is a combination of billet wheel and the 13 blade turbine wheel.
The Out of the box powermax lowest price I have seen is 1175.00 and no core charge and depending of year and condition of stock turbo 250.00-400.00 is what you can get for one so 1175.00 -400.00 = 775.00, if you want a billet wheel in it to spool faster and flow more air add 240.00 + 775.00= 1015.00. Warranty same on them, and the powermax is new.
The powermax has a 70% chance of working on stock injected truck and the MTW has 98% chance, with bigger injectors and tuning the powermax goes up to 85%, put the billet wheel in the powermax and it will go to 95-96%.
Now how the hell can I know all those numbers, I would call B.S. but there are reasons. Ready to learn something? so here is what I have learned taking that many turbos apart including powermaxs. The 03 stock powerstroke turbo has the same turbine wheel as the powermax, exactly the same, interchangable between the two. Yes if you put a MTW stage 1 compressor housing on a 03 powerstroke turbo bam powermax.(and with a billet compessor wheel) the 04 turbo use a 13 turbine wheel which is not interchangable but exducer and inducer are same size as the 03 turbine 72.5mm/66mm. After that the 05-07 turbos whent down in size in both compressor wheel and turbine wheel(compressor 57mm/82mm and turbine 72.5mm/64mm) That's why a 03-04 turbo runs better and trucks are faster than a 05-07 turbo.
Now just when you thought ok I get it, nope the 05-07 trucks have a hard time running a powermax, slow spool and high egts at cruise, on stock injectors. The reason is because the powermax is a bigger turbo and not really what I call a stock replacement, because it will need tuning to run right. The turbine wheel is so big and due to the compressor also being bigger that the 6.0 liters have a hard time in getting drive pressure to turn it. So VGT duty cycle needs to be closed more and bigger injectors also help in spooling the powermax on a 05-07. The 03- 04 truck are not as bad to run a powermax since the programimg on the ECM was made for a bigger turbine wheel.
I came along and I put a bigger compressor wheel with the smaller turbine wheel of the 05-07 and the surging issues were due to the cast wheel paired with the the smaller wheel. The turbine wheel would spin the compressor too quick and cause the surge, by switching to a billet wheel I gained surface area, more air flow, and lighter quicker spool. That pairing is very hard to beat, the stage 1 is extremely fast spooling, way faster then the powermax, and still supplies the air flow. Bigger injectors also aid in spooling a turbo faster so MTW stage 1 with bigger injectors will out spool a stock turbo, and is a blast on the street.
The big VGT turbos stage 3 and 4 are in a state of getting the tunes to run right in them. The turbine wheel I use for the stage 3 and 4 are a gt40 wheel and are much bigger then the gt37 wheel, and the powermax wheel which is also a gt37. The size of the wheel is causing the same problems as the powermax has on the 05-07 trucks but it is so big that it also effects the 03-04 trucks. Even with big injectors to help in spool the turbo needs tuning to straight it out, what people don't know is that with the tuning being develope by tuners and me working together to figure it out it will also benifit the powermax.
I have nothing against the powermax and think that it is a good turbo, but just wasn't thought out enough about how it was going to act on the 6.0 powerstrokes. Performance upgrade such as ported intakes, aftermarket intakes to get the air in will help out alot with the powermax, and also the MTW turbos.
There is a lot more in info I could get into but I think that is enough for now. Thanks and lets keep the 6.0 powerstroke running hard. Any other questions about the VGT 6.0 powerstroke post on here and I will try to answer them.