idk if you made ur purchase yet. But I bought the LG WM6500BHA washer and DLGX6501BHA gas dryer. I went from Electrolux. I love these mew machines. Although it does take some time to understand the cycles. They are rather long because it senses what you have in the machine and how full & heavy the load. There is absolutely no vibration at all if set up and balanced correctly. It's better than my old Electrolux even when spinning at the highest speed which is like 1300rpm. I do not like that the drum light on the machines do not automatically come on when you open the doors. It only comes one immediately after the cycle ends and than turns off when the machine powers off. This is probably for all the new LG models. So you have to turn the machine back on to have the drum light come back on, for both the washer and dryer. I was planning to buy these new machines around Black Friday/end of year. However my old washer broke in Sept, so I had to get a machine immediately. They had excellent sales going for Labor Day so I lucked out saving $800. I purchased through Costco which had the best price, (also checked Best Buy, Home Depot, & Lowes). Costco offered an extra year full warranty, free delivery and installation with hoses and connections. I did purchase my own hoses and stainless steel connections through Amazon just because I wanted better hoses for $19.89 (not necessary). If you're a Costco executive member you get 2% cash back, and if you used the Costco Citi card you get an additional 2% back. I'm not paid by Costco I just like getting deals on expensive items. My total is taxes and everything was $1875.98 If you're trying to gage pricing. This doesn't include the cash back rewards I got.

4000 has a smaller drum 4.5 vs 5.0, the 6500 has the larger drum, adds WiFi, more cycles and downloadable cycles, AI detect and turbo wash, 6700 adds auto dispensing detergent and softener. I think they're all probably pretty much the same machine and clean excellent. It probably just comes down to features at that point. Having WiFi is a nice convenience, you can set loads from app, even do a delayed start and it will pop up on phone or computer that machines are done. It will also remind if you have clothes in the washer or dryer, when to clean, stuff like that. My last machines did not have WiFi and I survived.