We won't know for sure until we have the device in hand. But this will use a Qualcomm SoC (originators of the CDMA standard) with all radios, including LTE, on the same chip. Thus its low-level firmware should be simpler and with less chance for bugs and translation errors. Not to mention that you won't have to worry about I/O bottlenecks between separate chips. The radios will use less power and have more efficient communication with the rest of the system, so yes I would expect this phone to be very good in terms of signal strength and quality.
I had a Droid Charge, and after all the issues I had Samsung themselves decided that their chips weren't ready for LTE yet. A company as successful as Samsung learns from their mistakes, and obviously Exynos 4 chips were not performing adequately with LTE, so they would logically go with the very best solution available. The Nexus doesn't really fit in to this argument, since it was designed and spec'd by Google, not Samsung, and they didn't really have CDMA in mind. Samsung pretty much had to take the Google-designed GSM version, shoehorn a CDMA/LTE radio setup in there, and hope for the best.
All that to say that I would expect the SGS3 to be more power efficient than any other LTE device so far, as well as be one of the best in terms of signal reception and quality, due to the S4 SoC. But ultimately we won't know until we get them in our hands, will we?