I’d say stainless steel makes sense if you want something that feels more permanent under the sink. I switched away from a cheaper plastic setup mostly because I was tired of worrying about cracks, overtightening, and whether the housing would age badly. The cartridge still matters a lot, of course, especially if your water has chlorine or chloramine. When I was looking around, I found this chloramine filter cartridge while comparing systems, and what caught my attention was that their undersink unit is stainless steel but still works with practical carbon block filtration. I’d check faucet compatibility, cartridge size, and whether the filters are NSF/ANSI 42 certified before choosing.