Both are reality tv shows in Japan. They both have wholesome content and couples that I enjoyed watching.

So much went on in both series, all the side characters and how it went so well with the storyline remind me so much of how similar this series is. Although if you're looking for a bit more of a romance, I think LST has it. SSS is about the ML

The first thing that came to mind was Chinese Paladin as I was watching Sword Snow Stride. These were the closest similarities I can find:

Lots of traveling
A bit of a love line going on
Wuxia

Because of the wholesome love story between the leads, they remind me of each other. Koi Desu is just a bit more exciting and funnier and Forever Love had a bit more typical Asian drama and conflicts to overcome.

It probably because I watch them around the same time but I felt they had a very similar vibe. They were family friendly series to watch. Both are about problems the female leads goes through before falling in love with ML

Both are dealing with palace politics wanting more with each episode! The only difference is that Rise of Phoenixes has a bit more of a love story attached to it.

Both series revolve around a case that isn't solved and deal with palace politics. I felt on edge wanting to know what was going to happen with the next episodes. Both of them gave me the same excitement! The only difference that I spot right away was that The Longest Day in Chang'an had amazing cinematography and I love the coloring. Gotta admit it captived me on the first episode therefore I couldn't stop watching. I didn't know what was in store for me when I started both series.

The love between ML and FL reminds me of Akai Ito. Something holds back ML and because of that he doesn’t pursue FL right away.

Both series start out with an idol group that is no longer popular and no one really pays attention to anymore. I believe both FL are the leaders of the group, they struggle to make it in the entertainment world but as they meet headstrong ML, slowly ML starts to have feelings for FL.

FL disciple of ML
Both ML made decisions not to get married but that slowly changes over time because FL
One and Only just has a slow-burning love whereas in Pearl Eclipse I felt ML was a bit more aggressive.

Virtual world and Love, at least that was the start of the story!! Love crossed has a bit more complex storyline with a twist whereas Holo Love was just a common love storyline with the FL lead not being able to see faces but she can see ML.

Both FL gets a new identity as they plot for revenge for their family. Both FL comes from royal family taking on the identity of her maid or family friends identity.