My opinion based on owning both an EVM15L and a Kappalite 3015:
The 3015 goes MUCH lower and will take much more of a beating down low. An interesting thing people don't often realize is that the 3015 is not voiced with as much bottom beef as most 15s wind up being in standard bass cabinets. It has a very smooth low end roll off with almost no upper bass bump in any reasonable sized cab and tuning situation.
So if you want it to sound authoritative in the bass/midbass, you need to boost it.
Similarly, it has a snarly bit of distortion up on the top end of its range that needs to be eq'd out for an old school tone.
My opinion is that the best ways to achieve this are a lowish crossover to a horn or midrange driver, the VLE knob on a Markbass head, OR the tone knob on a bass. EQ can certainly achieve it, but many heads simply cannot effectively cut in the right way to thicken the tone up without deadening it.
Anyway, I think having owned them both you can easily get the tones of the 15L out of a 3015 if you are well educated about tone shaping. That said, I actually do not mind the snarly upper mids of the 3015 - they are not really that bad and the speaker sounds OK flat to my ears.