well the larger the texture file, the more maya has to do to process it. if you have a smaller texture file and then tile it in maya, maya is just reusing the information... in order to make sure the texture doesn't look bad tiled, you have to take it into photoshop or another photo editing program and pay attention to the borders. there's a tutorial here
that might help. they're all over the place if you just know where to look.
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