in function:
many becketts are good.
many needle wheels are good.
airdriven are good but there aren't many
in my opinion, standard venturis are not. the bubbles they form are way too big. most hang on skimmers are a standard venturi type thus they aren't real great.
the Aqua C is not a standard to my understanding... i have never owned one.
also there are downdraft skimmers with media in the tubes that will break up the bubbles and they apparently do good job. ETSS makes some good examples of these and i know of more than one reefkeeper that swears by these things.
the action inside them looks great and that is all i really can say about them.
to maintain:
between becketts, needle wheels and standard venturis...i don't know how to respond.
needle wheels and powerhead venturis are more reliant upon a clean, debris free intake that is often submerged in water... whereas a beckett just has an intake valve that is very accessable and easily cleaned at any time.
but then a beckett is larger and i would think harder to clean the interior of the skimmer... but i have never owned one so i couldn't say for certain.
air driven are pretty tempermental. they require constant fiddling to stay dialed in. they also need regular airstone changings.
economically:
becketts are spendy.
i would look at something like a Precision Marine model if i were to buy one.
this is still about a 400 dollar investment.
by some, needlewheels are said to be spendy in the bang for the buck and i don't fully agree.
i bought an economy series Euro-reef and paid 246 dollars.
i did the math and found that the body and wheel cost me about 100 bucks after subtracting the pump retail.
that seems acceptable to me, even if it is an injection molded plastic chamber.. the collection cup is the same as the C series and the function is identical.
Turboflotor makes a very reasonably priced needlewheel although it won't perform like a Euro-reef, Deltec or Bubbleking.
standard venturis are cheap.
airdriven are very inexpensive as they don't need a water pump to operate them. Lee's makes one that i picked up as my first skimmer for ten bucks! i already had an air pump.
the energy you save using one of these would buy your airstones.
lowdown:
becketts are noisey and many take up a lot of space although they are easy to maintain and really perform.
needlewheels add heat to the water and a replacement wheel will put you in the poorhouse but they make a good foam at a quieter decible level.
standard venturis are weak unless they are a downdraft design.
airdriven are ugly without a sump and tempermental although they do a great job at keeping the water clean when functioning and also make very little noise.
anyway, there are some of my opinions... it might help if we new exactly what size tank you were planning on.