@fify-- Both simvastatin and lovastatin cause muscle pain, so in that sense, it doesn't matter which one you're on.
But I have heard that simvastatin works better than lovastatin. So if simvastatin is working to reduce your cholesterol right now, you may not be as happy on lovastatin.
On the other hand, my friend was on simvastatin and she lost a lot of weight on it. She became underweight. I don't think that lovastatin has a side effect like that.
I think they both have their advantages and disadvantages. Neither are perfect drugs unfortunately.