You really should go for Lee Kesler enthalpies. I do not have hard evidence in this post (literature comparisons or so), but even a quick search on the internet will yield literature references that confirm this. There are also conversations I had with users that are a pretty good indicator. Some people emphasise the benefits for cryogenic systems, others recommend Lee-Kesler more generally. There is also some recent work I did on modelling turbo expanders that clearly showed that the Lee-Kesler enthalpies matched vendor performance data much better.
And, there is a little bonus that is probably not so well known: When you select Lee Kesler enthalpies, HYSYS will look at your stream composition and if it is all water, it will use the ASME steam tables. Even at standard conditions, the error on PR EOS duties is about 3.5% and this grows worse as you go to higher pressures. So, if only for this, selecting Lee Kesler Enthalpies is a good thing to do.