I am a big fan of these modern, no border type quilts. Having said that, I almost always add borders because I never seem to think the quilt is big enough, thereby making it more traditional.
As an answer to your question - this is such a personal choice. Modern = no borders. Traditional = borders. And, is it big enough? You have an oversize lap right now. Do you need or want a lap, or do you need a twin? Borders will up the size.
Let us know what you decide to do.