The Le Meridien and the Sarojin are both located on Pak Weeb Beach. The Le Meridien stretch IMHO is nicer; there is one beach restaurant about 200 metres from Le Neridien and three within same distance from the Sarojin. The two resorts are about 1000 metres apart ( abeautiful after meal stroll).
The Sarojin has its own boat which takes you on trips to the Similans, but like everything else at the Sarojin is much more expnsive. There is a Dive Shop and AsianTrails Tour Shop at Le Meridien where you can book dive trips more cheaply but there are many dive shops in Khao Lak Town where you can book more cheaply.
See links at http://www.mykhaolak.de/dive-center/...ve-center.html In German but the pictures speak for themselves and those with their own websites have English versions.
The Sarojin is a smaller more intimate resort and if yyou look at the TripAdvisor Forum you will find several threads about Honeymoons on the Thailand, Phang Nga Forum. Though much bigger the Le Meridien has a greater selection of room types and plenty of space to be on your own, if you understand me.