I have a LS5-II now and own one VK30SE before. They are all excellent preamps. BAT is more accurate and ARC is more lush with tube glare. So it depends on your taste. Md. Butterfly vs. Carmen.
BAT has a ss type of control on bass and like a well-behaved human, it can be too revealing for some bad recorded CD's. ARC is smooth, bold, and more forgiving, it can be warm for some people. I keep LS5-II becasue it has 12/30 db gain, that helps when using with phono stage for low gain cartridge. I prefer neutral toward slightly warm type of sound. But some people may like the other way. Also Sonic Frontier 2SE/3SE is pretty good, sound wise falls between BAT and ARC.
BAT has a ss type of control on bass and like a well-behaved human, it can be too revealing for some bad recorded CD's. ARC is smooth, bold, and more forgiving, it can be warm for some people. I keep LS5-II becasue it has 12/30 db gain, that helps when using with phono stage for low gain cartridge. I prefer neutral toward slightly warm type of sound. But some people may like the other way. Also Sonic Frontier 2SE/3SE is pretty good, sound wise falls between BAT and ARC.