I will share my experience and opinions with the understanding that they are just that, and like all things, tone and play ability are somewhat subjective.
If you want a super racehorse type bass, Wal probably shouldn't be the first choice, though I do find their 4 strings to be incredibly playable for me. The string spacing feels good, there is no excess string tension owing the great design, and while some might not love the deep neck profile, I find that it works well for me and plays pretty fast. But Wals don't feel sleek per se- they are substantially hefty instruments.
As for the tone, Wals do what other basses don't because each pickup has its own filter. This means you have a tremendous tonal range from eliminating all the high end to get the tubbiest dub sound't you've ever heard, to that very active "I have water in my ears" sound, to the grunt of Flea's sound on BSSM.
If you wanted to come close to what I consider the sound active sound of a Wal you could accomplish that by using a bass with filter-based electronics. It certainly won't sound it won't have the same circuit and pickups (also a huge part of the Wal tone recipe) but it would give you a similar ranger.
For me the ultimate poor-man's Wal is the Heartfield DR series. It's a much simpler filter and there is only one global filter for both PUPs, but it does give you that signature active tone.
Other basses that feature filters- the older Ibanez SRs with the Varimid electronics and Alembics.
Lastly, there is an aftermarket preamp called the ACG EQ-01 deigned by John East for
@Skelf at ACG. It is modeled after the Wal preamp and does give you an individually adjustable filter for each pickup. It is an expensive unit (about $360) but worth every penny, especially if you want to port the tone and flexibility of a Wal into a different bass that is more familiar to you or more to your liking for playability. I dropped one into a John Suhr era Fender DLX JV and it is awesome. I wrote a review about it here:
Fender Suhr era DLX J V + ACG preamp = KILLER Bass!!!
Hope this is helpful. Again, just my experience but hopefully this information is of some value to you.
Good luck.