I like the SF UL much better than the DS UL, but is less a true UL than the DS UL.
The DS UL has a definite dead spot in the flare and JLs need careful timing on the pull back to the fade. IIRC Frazer's was a one off raffle prize and predates the release of the DS UL by a few years. It may well be that it has slightly different flying characteristics to the production DS ULs. The SF UL in my view is a better all round kite but won't fly as low on those real low wind days.
We all like different things in our kites, so the best bet is try and find someone one has either or both of these kites and try them.
... or take a punt on a Vortex UL.