Love is hard to define. Here's one reason.
We all know what gravity is: it makes bricks fall on our feet when we drop them. It works the same for everybody -- it is an objective reality.
Love does not cause bricks to fall on our feet, and we can't weigh it. It is completely inside the mind -- it is a subjective reality.
Therefore, you define love inside your own mind and only in your own mind. I define it in my own mind. Your love is not my love.
So asking whether poly love is different from mono love is almost crazy! We don't even know if George's mono love is the same as Fred's mono love, or for that matter from the love of one turtle for another turtle.
It's like asking whether someone who thinks Beethoven's music is beautiful has the same feelings as someone who likes Beethoven and also Brahms. First you have to figure out the subjective concept of beauty, and it's just not the same for different people.
For myself, I love my poly girlfriend as much as I have ever loved any woman. If and when I find another lover I expect I will love them both in much the same way as I have loved anyone.