What private server is best for introducing a completely new player to WoW?

Hi!

I want to introduce my sister to WoW. I tried doing this about a year ago with a trial account on retail but she thought the new player experience on retail was very confusing and overwhelming, and thus quit.

I realized that Classic WoW (or an earlier expansion) might be a better, simpler introduction for her. However, I do not want to burn a bunch of money on two monthly subscriptions to play official Classic WoW, on something she might not even like in the end.

The plan is to start playing on a free private server first before committing to any sort of subscription.

My question is, what is the best private server for this? I am looking for a fairly Blizzlike experience in either Classic, TBC or WOTLK. It also needs to be well populated! Half of the WoW experience is the community itself.

The two servers I currently have in mind is either Project Ascension (Bronzebeard) or Warmane (WOTLK).

I have never played Ascension before but I have heard that it's a well-populated, high quality, Classic WoW server. However, I also know that it does have some extra addition and extra game systems slapped onto it. I am okay with this as long as these systems can be ignored or aren't too disruptive to the Classic experience (or are immersion breaking).

Or should I go with WOTLK on Warmane? I used to play on Warmane way back in the day (during Cataclysm), but back then the server was quite buggy. How is the server quality and experience nowadays?

Do you have any other suggestions? Remember, the server needs to be well-populated.

Thanks!