Hi wendy ang: Hope im nt too late to provide my comments here.
I went to both places b4. In terms of d chalet itself, both r v similar, almost like twins! V nice & comfortable. As both r similar, it now depends on whether u want to do an indoor or outdoor ROM.
For outdoor, I will recommend SAF Seaview Chalet for ROM cos it has nice view. In fact, I had my ROM there last yr. Moreover, it's more accessible for guests who don't drive as there is public bus from I think Tampines interchange & it stop just outside d gate of d chalet. I hav pics if u r interested to c den u will hav a beta idea.
For indoor, NSRCC wud b a beta choice esp if u hav alot guests. There is more room for them to stand outside d chalet cos there is no staircase leading to d chalet. For SAF Seaview, each chalet unit has a staircase leading to it so it wud v cramp for ur guests IF u r putting a buffet line along d balcony.