Not familiar with that stuff. I'm sure it's good, but I get Permatex grey RTV for free so that's my sealant of choice when I need to use something in a tube.
But I'm still partial to using gaskets when that's what was in there before- there's always going to be squeeze-out and I like to keep the inside of my rad and water jackets as clean as possible. Also making a gasket is ridiculously easy if you use the hammer method. You just stick your gasket stock to the part you're sealing with hi-tack, take the ball peen end of your hammer and *gently* taptaptaptaptaptaptap around each edge- the edge will cut the gasket perfectly for you. I've had to do it a bunch of times at work and twice on my own stuff.