Maximus is my choice. We've used both, and either will work great. The only deciding factor for me is that Liquid silk contains Dimethicone, which may harm silicone toys. We used it for a long time before we knew that and never saw any ill effects, but it is still something to consider. Also, they both contain parabens if that is a concern for you. If the list of ingredients doesn't sway your decision, the only other consideration I have is that Maximus is a little thicker. That makes it better for anal in my opinion. Still, either lube works great.
It somewhat depends on how you plan to use it. Maximus is thicker and can be used vaginally but is generally used for anal. To me, Liquid Silk gets a little sticky but I've never ad a problem using it with silicone toys.
I haven't tried Liquid Silk so I can't comment tell for sure but I have tried maximus and based on what I've heard it depends on what you want to use it for. Maximus is thick, defiantly thicker then liquid silk, so it better for anal.