I prefer the Pen to SL in Manila, although both of them are among the weakest offerings within their respective property portfolios.
I don't like the dark and gloomy decor of SL, although it might be a matter of taste. Service at Pen was slightly warmer and more attentive. The SL isn't too shabby in this aspect either.
They're across the street from one another, so location wise, it's a wash.