You'll find lots of different opinions on this subject, and it really has been throughly covered more than once on this forum.
If a factory rear locker is important to you, 98-99 LC.
If ATRAC/VSC is important to you, or the 2 pinion front diff concerns you 2000+.
If the reported trans problems in the 00 MY concerns you, any year but 00.
If you have to have a modern aftermarket sound system, non-nav 98-02.
If you have to have LATCH child seat mounting 2001+
If you want the 5spd, 03+.
If you like VGRS, 03+.
If you like vvti, an 06-07.
If you're concerned about the reports of vvti being an interference engine, 98-05.
If you think the name change from ARACO to Toyota Auto Body affected quality, 98-04.
If you like AHC and memory seats, a LX.
If you hate the body cladding, afraid of AHC or you're afraid of being one of those snobs in a Lexus, a LC.
A sample of similar threads:
https://forum.ih8mud.com/threads/what-year-preferred-is-best.907967/
what is the best year of lc100 or lx470 to get?
Which 100 Series or Lexus to buy? (FJ40 owner
What would you do?
Best year 100 to buy ?
I'm comfortable driving my stock 06 LX or my son's modified 00 LC. At 9-18 years old, I'd argue that vehicle condition and history would be more important to me than model year, but all things being equal I'd prefer 03+ and a mild preference for the newest I could find. I prefer the the looks of the LC but like the additional features in the LX.