I can't answer for Marsha, but I moved from the ProTime to the ProTime 3 to the InRatio.
The ProTime to InRatio move was fairly easy. The ProTime, while possibly more accurate (possibly) than InRatio or CoaguChek S or XS, requires a lot more blood than the InRatio or CoaguChek meters, and uses strips that must be refrigerated. It's a bit of a pain getting the extra blood needed for the ProTime and, again, there's the issue of refrigerating the test 'strips' (which they call cuvettes). Also, if your strips expire, the meter won't take them (the InRatio will gracefully use a strip that's up to a few months 'expired' - but quality controls built in will indicate if the strip is still good.
The InRatio just seemed to be easier to use than the ProTime or ProTime 3 -- at least, for me, it was easier. The InRatio strips don't require refrigeration unless your storage temperature exceeds 90 F (as it does every summer here).
CoaguChek XS strips also don't require refrigeration (but may have some upper temperature storage limit). I don't know what the CoaguChek XS will do with an expired strip. The CoaguChek XS may be just slightly easier to use because you can put your incised finger (and its big drop of blood) onto the side of the strip and capillary action will bring it into the strip for testing. (With my InRatio, sometimes it's not easy positioning the drop of blood onto the small dot on the strip - I sometimes use capillary tubes made for that purpose).
The InRatio 2 is supposed to give you test results more quickly than the original InRatio. It uses icons instead of text, which makes it easier to sell the meters internationally. I'm not sure if the icons make it easier to use than the text or not - I've heard both opinions.
(One thing to consider -- some facilities 'retire' their perfectly functional meters once they've been fully amortized (3-5 years) -- which may mean that InRatio and possibly CoaguChek XS meters may be available for considerably less than retail. I got my InRatio and ProTime meters on eBay -- and they've been functional and accurate. One day, perhaps, I'll also try a CoaguChek XS -- but I'm still quite satisfied with my InRatio).
Another thing -- I've had questions for Alere, which now owns InRatio, and support has been excellent. I don't know about Roche support.
One more thing -- DON'T buy a CoaguChek S. It was discontinued a few years ago, and Roche will stop supporting it very soon. You may not be able to get strips that expire after early next year. Also, the CoaguChek S was not made for home testing and quality control is not built in.
You should be happy with either the CoaguChek XS or an InRatio (or InRatio 2). All are made to accurately run tests (and all may have more deviation from lab tests the higher your INR gets).
Oh -- one more answer to 'why did you choose INRatio instead of CoaguChek?' -- in my case, the answer is simple. I was able to get an InRatio on eBay at a very good price. If I was offered a CoaguChek XS (instead of an InRatio) at the same price, I would probably have gotten that instead. Both are good meters, from good manufacturers, and the cost per test is pretty comparable.