Powerflight is a high performance twin vac portable with 500psi pump. Excellent reputation in the industry. The Wonder Wand too has an excellent reputation.
The Alltec Advantage is a twin vac 135(?) psi machine and is a solid workhorse. It would not be suitable for any patio tile and grout cleaning.
Were you thinking more of the Alltec Advance? This is similar but with a 600psi pump.
The Prochem SteemPro is closer in spec to the Advantage, so inferior to the others you've mentioned.
IMO, you need at least 1000psi for tile and grout cleaning and perhaps as much as 3000psi for patios. Any less and the job becomes too slow to be a main line profit earner for your business.
Tools and other attachments within our industry are, on the whole, interchangeable. Sometimes you may need to change a QD fitting from male to female (or vice versa) to make different brands work for you. If you wanted to use a WonderWand with another brand of machine, you'll need more than 200psi, preferably 300psi plus.
If you have a smaller vehicle, the Alltec machines are a little more compact.
If I had to shoose from the above list, The Powerflight would just about nudge the Advance, but I'd be happy with either.
Safe and happy cleaning
Ken