Senka no Maihime Vol. 2 Updated

That is not for me to decide (kinda). It depends on where the ebooks are purchased. I usually purchase from Kobo, so it has pretty much the best quality illustrations available (Aside from premiums). Some ebooks shared by others maybe be bought from other sources which has lower quality illustrations. Different sources = different prices/satisfies different needs of the purchasers, etc.

If you really want HQ illustrations, you’ll have to wait for someone else to purchase the HQ books and share it, or purchase the books yourself.