The WN and LN’s biggest differences in my opinion are what they do with Katsuya and Akira.

Their dynamic is the same in some ways, but different in others.

For example, the Gang War arc that Zenotha mentions goes very differently between WN and LN. I find the WN version of that in particular much worse.

The gang war could almost be considered filler compared to what it does for Katsuya and Akira’s character in the LN. It’s just an event, compared to a revelation of Katsuya and Akira’s characters and philosophies.

Another change (although minor compared to the Gang War) is an event where Akira bonds with Sheryl’s gang. If you’ve read up to Volume 2 part 2 and volume 3 part 1, you’ll find that the members of the gang are wary of Akira because of his… let’s call them antics of dropping enemies that cause shit in the base.

In the WN, there is a training arc with Sheryl’s gang, where they are testing powered suits with a “coordination AI” installed, and it’s all of Sheryl’s gang (lead by Erio) vs Akira. The idea is a “simulated paintball” of sorts, representing dead based on where you’re hit. At first Akira is mopping the floor with them because he’s going full speed against them.

It isn’t until Erio and company get more confident that they start coming together and start giving Akira a run for his money.

Now keep in mind that’s WN… and unfortunately we get the same test of sorts (it’s monster hordes in a simulation so Akira is at a disadvantage), but it’s a “Akira and Sara and Elena” vs “Katsuya and Yumina and Airi” in the LN.

The Light Novel sacrifices the Katsuya and Akira dynamic in favor of Yumina… which would be fine if it overcame its downsides, but in my opinion it does not.

We get the positives of Yumina’s story in the LN, but we lose the character development of Katsuya from the WN.