I personally love the Grand Prix jackets! They are super light weight and breathable as well as they are machine washable! They also come in a variety of colors and styles so if your a hunter or a jumper they safe choices and fun yet classy choices for you! Also they are a great price for the quality! If your willing to spend more i would recommend a Charles Acona. They are completely custom so you can get any color combos and they are still lightweight and breathable! Hope this helps!
I have tried so many jackets and the only one that I have found to love is the Manfredi Airflow Jacket. The cut is very fitting but fabric is extremely stretchy. And the best part comes in long sizes which are actually long enough. But of course you have to pay the price for perfect . (I am 5'10" and on the skinnier size for my sizing info )
Depending how much money you want to spend, caballería Toscana is quite expensive but are amazing jackets, I also really like horse pilot they aren't expensive. Spooks are good and so is kingsland. There is also another brand called animo which is an amazing brand but also quite expensive