Brake response is spongey post-brake lever upgrade
You get more sponginess for one of two reasons:  More mechanical advantage (meaning the lever must move farther to move the pads a given amount) or more flex somewhere -- either in the levers/pivots, or in the cable and it's mounting.

(The cable mounting can be an unsuspected source of flex if the cable doesn't approach the mount squarely and the first bit of lever motion is "spent" just forcing the cable to line up.)

There's also a psychological factor -- activating a lever in a different direction or with different parts of your fingers can seem to have more/less flex.