I'm one of the Chisel devs.
My biased view is that iterative development with Chisel, to the point of functional verification, is going to be faster than in a traditional RTL language primarily because you have a robust unit testing framework for Scala (Scalatest) and a library for testing Chisel hardware, ChiselTest [^1]. Basically, adopting test driven development is zero-cost---most Chisel users are writing tests as they're designing hardware.
Note that there are existing options that help bridge this gap for Verilog/VHDL like VUnit [^2] and cocotb [^3].
For libraries, there's multiple levels. The Chisel standard library is providing basic hardware modules, e.g., queues, counters, arbiters, delay pipes, and pseudo-random number generators, as well as common interfaces, e.g., valid and ready/valid. Then there's an IP contributions repo (motivated by something like the old tensorflow contrib package) where people can add third-party larger IP [^4]. Then there's the level of standalone large IP built using Chisel that you can use like the Rocket Chip RISC-V SoC generator [^5], an OpenPOWER microprocessor [^6], or a systolic array machine learning accelerator [^7].
There are comparable efforts for building standard libraries in SystemVerilog, notably BaseJump STL [^8], though SystemVerilog's limited parameterization and lack of parametric polymorphism limit what's possible. You can also find lots of larger IP ready to use in traditional languages, e.g., a RISC-V core [^9]. Just because the user base of traditional languages is larger, you'll likely find more IP in those languages.
[^1]: https://github.com/ucb-bar/chisel-testers2
[^2]: https://vunit.github.io/
[^3]: https://docs.cocotb.org/en/latest/
[^4]: https://github.com/freechipsproject/ip-contributions
[^5]: https://github.com/chipsalliance/rocket-chip
[^6]: https://github.com/antonblanchard/chiselwatt
[^7]: https://github.com/ucb-bar/gemmini
[^8]: https://github.com/bespoke-silicon-group/basejump_stl
[^9]: https://github.com/openhwgroup/cva6