Are pump res. combo's worthy of upgrading?

[Smalltimer]

On my quest for ultimate power, I've come across the no so good plumbing job connecting my pump and Res.
And so I've been eyeing something a little more modular in hopes of optimizing my flow rates and cleaning things up in the process.

And so I wanted to ask if anyone knew whether a pump/res combo would be just as good as a discrete res and pump setup?
ie, any drawbacks to know of, brands or tops to avoid OR even a batter alternative altogether.

PS. I have no interest in practicality as this is an Xtreme system designed to squeeze every last bit of cooling performance.

[stren]

They can be, but some aren't designed well and are a compromise e.g. Aquacomputer and XSPC tube res with d5's were better individually than as the combo. There's no reason they can't be as efficient though.