The right gear can provide you with an advantage on a long distance hike. However, I have seen many successful people use a lot of different gear proving that what is right for me is not necessarily right for you.
For example, someone recently asked me about what pack to get. I've only used ULA and Hyperlite Mountain Gear packs and much prefer HMG over ULA. However, I've seen enough people rave about Gossamer Gear, KS Ultralight, and Pa'lante packs that I believe they are worth researching at the very least. Also, someone I met on the PCT made his own pack and it performed so well that he decided to see if he could make a business out of making packs for other long distance hikers and started Chicken Tramper. I personally like what I see and plan on trying it out as it appears to have some advantages over the packs I've used in the past.
For most gear items, I could do something similar. Ask me what tent to get, I would give out several different options while mentioning that the tents I use are no longer made. Ask about a sleeping pad and I would have to tell you about several options including one I hate but have seen many other people love. I used to tell people which rain jacket to get until I saw three other rain jackets that I think are in a similar or even superior performance level.
However, there are two gear items that worked so well for me that I have to recommend them. The first is my sleeping quilt. Once again, I have seen other people use and love something different, but this sleeping quilt is so superior to any other sleeping bag or sleeping quilt I've used that I think its worth recommending. Also, I've heard others rave about it the same way I do providing me with more validity in my belief.
My Custom Enlightened Equipment Enigma 40F Sleeping Quilt.
My Enlightened Equipment Enigma custom made quilt worked perfect for me. I used a 40F quilt that only weighed 12.1 oz. and kept me warm enough to sleep even when the temperature dropped into the teens. The one disclaimer I should use is that I sleep incredibly warm, so I don't recommend that you use a 40F quilt. Most people will want a 10-20F quilt. Getting a custom quilt allows you to size it based on their recommendations so that you don't have extra dead space. Even there, I used a shorter and narrower quilt than recommended based on my height and sleeping habits and I would not change my choices. This is my favorite gear item.
Second, my wind jacket I fell in love with so quickly that I don't remember how I could tolerate not having the thing. When I started to hear everyone who owned that wind jacket make similar statements, I felt like I could easily recommend using the jacket.
My MontBell Tachyon Wind Jacket on a windy morning at Mt. Baden-Powell.
The only bad review on the MontBell Tachyon Wind Jacket I saw was a lack of durability, but after hiking over 7,000 miles with it, my wind jacket still appears ready for more long distance hiking.
My wind jacket weighs a little over 2 oz. and it replaced a baselayer top and beanie from my gear which combined weigh well over twice as much and it provided superior and more versatile performance. As soon as I get a little chilled, I go to the wind jacket. If I'm at camp and want to prevent mosquito bites, on goes the wind jacket. It works well in wind and even light rain. Even if you get it wet, it can take mere minutes to dry. Literally, several times I hung dry my wet wind jacket and found that it dried faster than my clothes in the dryer.