Looking at the data sheets, it looks as though it's closer to a 5751 with Gm of 1325 vs.1200, both have a u of 70 and plate resistance 53k vs. 58k. Also bias voltages are close as well. Heater current draw isn't an issue either with them being very close to each other. I personally like the different 12A_7s because of the variety and not having to replace the socket. Others may disagree.