I have and use both Live Suite 9 and Cubase 7.5, and while I really like Live’s elegance and believe Ableton consistently comes up with some cool and innovative ideas, Cubase 7.5 is just a ridiculously full-featured product.
Also, until Cubase 7.5 came out, Live might have had the edge on Cubase in terms of ease of use when working with virtual instuments (like the Native Instruments stuff), but with Cubase 7.5 I think they’re on equal footing in terms of flexibility with plugins (and Cubase has always offered far more power and flexibility when working with external hardware instruments).
Also note that Live doesn’t support VST3, so its plugin compatibility isn’t 100%, at least not on Windows. I think all the NI plugins are covered, but numerous Antares and Waves plugins either aren’t supported at all or only offer limited functionality on Live, for example.