We're doing the opposite - traveling from Universal to the MK one day during our upcoming trip (staying at PBH at Universal). We decided to hire a limo for the RT - $70 + tip. They will pick us up at our hotel and take us to the Contemporary resort; we'll make our way to the MK from there. After Wishes, we'll return to the CR where our limo will take us back to PBH.
The limo cost, from what I've read, is about the same as a taxi - but no hidden costs like getting stuck in traffic or getting a taxi that takes the long way back. Plus we know it will be there for us - one less thing to worry about.