In todays business climate, OEM's change their way of manufacturer, sources of castings and foundry items, and optimize and/or cost reduce their designs so that there is no guarantee that the two new pumps would be 'drop in' identical to the older pumps.
That said, several good points have been made, but the most important one was to analyxe the curves throughout the range.
Also, analyze how the newer pumps will be adjusted for wear during their lifetimes. The way they wear and are adjusted to compensate for wear, as well as their repairability (ability to be brought back to their original curves after significant wear) should be a factor in your selection process.
But to answer your question, I see different branded pumps running in parallel quite often, some successfully, and others not.
Be careful.
rmw