For me, B&H Photo Video (bhphotovideo.com) is simply the best.
An outstanding ecommerce website, with excellent product photos and descriptions, and truly useful reviews by a knowledgeable base of professional and enthusiast users. They flag reviews by members of their community and of reviewers who have purchased the product (from B&H). Another great thing about their product pages is a link to relevant accessories, not just any old accessory they might like to sell you, but items that will fit and are actually compatible with the camera, lens, tripod, etc. that you are considering. They have explicitly clear policies on shipping, return policy, etc..
I have found them to have an incredibly comprehensive range of electronics (not just photo/video) at competitive prices. Over a 10+ year period, I think the longest I've waited to receive an in stock product is two days. Dependent on product size and $ value, shipping on most products is free. I have have had positive experiences returning and exchanging products with no hassles or hurdles (read their return policies - they both honor and enforce them - unpack carefully).
This post is long, but there are two more points I want to make. One - if after reading their excellent product descriptions, you still have questions about a product or want to compare two or more similar products, you can call them and speak to an actual human being who is familiar with those products! Two - You can very easily sell or trade in your old gear if you want to upgrade or just offload seldom used gear. You never receive what you'd like for a trade-in from anyone, but I've found B&H to be reasonable and fair. (Type "trade-in" into their site's search box to access.) I have no link to B&H other than being a longtime satisfied customer. I have a more local camera store, staffed by nice people I'd like to recommend, but they simply can't compare on product selection (especially accessories), quality of website, and things like return policies. I never buy any electronic product without at least checking details on their website.