Having experienced many devices from both brands over the years, I concur with the summary @donquichotte posted above. That is generally how I hear the house sounds of each brand as well.
Luxman has a greater focus on resolution and speed, while not being overly fast or thin as some other devices can be. Separation and layering are strong points, as are imaging and soundstage expansiveness. It is a nicely balanced tone and fairly universally compatible as far as pairing with other components from different brands.
Accuphase does tend to have a more tonally rich presentation, with smoother and more relaxed feeling on the top end. Not overly dark, but somewhat mellow while still giving quality detail and resolution. Warmth is a big factor here, Accuphase has plenty but again does not go too far. This sound will pair extremely well with certain gear and not very well at all with other gear. So more picky than Luxman in this regard.
Someone brought up Esoteric which should always be in the conversation when it comes to top caliber Japanese gear. The older models could get overly bright and thin, but once they developed their discrete DAC solution that all changed.
Lastly, a somewhat lesser known but similarly capable Japanese brand is Soulnote. Tiglon Japan uses the top Soulnote equipment (plus a few Luxman pieces) in their quality control room where every single cable is tested prior to shipping out.
Is there any way to audition any of the devices you are interested in? That really is the best way when making a substantial purchase like that. Soulnote would be challenging but you should be able to find some or all of the other three brands from dealers in your area who can arrange a demo one way or another.
