For a Trane XL15i or XL16i system, is the 2/4TEE air handler with the builtin Clean Effects better or worse than getting the separate Clean Effects unit?

Pros and Cons?

Also, is it normally best to get the 2/4TEE air handler that offers the most cooling capacity that still matches the nominal tons of the outdoor unit and can fit in the space designated? Likely a lot more to it that that I suppose.

See http://www.trane.com/Residential/pro...ableSpeed.aspx as one source of my confusion besides the fact that I have gotten conflicting info from the salesmen and what I have read.

Thanks, Dave