suggestions about single or double tube buffers

Prices on new single or double tube buffers are about the same, so is there any reason to prefer one over the other? Also, any thoughts about quality between Yaqin and Grant Fidelity?
single tube buffer simply inverts phase. double tube buffer inverts and then re-inverts phase.
sonically, none is the best, but if you really need it, than purchase single one preferably with bypass switch so you can switch between modes.