It's so different that I still have difficulty recognizing horniness as such because it's still new to me.
First off, the physical sensation is different. Before, if I was really turned on I would feel it in my chest. Now I feel it in my face (similar to the feeling of blushing or needing to cry)
Also, the onset of horniness is different; the cues and thoughts that trigger it have changed and the overall onset is slower, which is another reason I have difficulty recognizing when it's happening to me. Before it would be like "I see something sexually arousing or a dirty thought crossed my mind and I'm instantly aroused because of that" and now it's more like "Gosh, I'm feeling in a pretty good place right now and wouldn't it be so amazing if something new and exciting were to happen to me and oh my god i'm horny 😳".
It also subsides much slower, too. Even if I try to take my mind off of it the feeling takes a while to dissipate. It's a more persistent feeling that can last for hours or, in some cases, days. The most accurate description I've ever heard is that it's like a "slow burn".
It's also just plain more … pleasant? When I'm horny I am on top of the world and vibing so hard. Like, before horniness felt more like sexual frustration and now it feels more like sexual distraction; I wouldn't mind being horny for days at a time other than it makes it hard for me to focus on my responsibilities.