Please remember it's a violation of forum guidelines to bump your own thread.
I bet no one bothered to answer because this topic has been discussed tens of millions of times, and performing a simple search using the forums built in search engine would generate so many answers/opinions/experiences that you could spend the next few years going through all the results.
If you read the forum guidelines and posting standards, the policy here is to use the search engine first and if you do not find what you are looking for, and you don't find an existing thread that is relevant enough for your question to go in, THEN create a new thread.
Just letting you know, this isn't personal, but this question so easily could have been answered without it's own thread.
Anyways,
Vaporizing it produces an IV-like rushing euphoria but is terrible for endurance/duration, you'll find yourself with your tweak pipe in one shaking hand and your lighter in the other shaky hand, the meth will be gone in a minute, and you'll be faced with the much harsher comedown that vaporizing methamphetamine produces.
Intranasal abuse while may not produce the intensity of rushing obtainable via other ROAs, but I think it's good in that it has a good balance of intensity:duration. It's intense and longer lasting with a smoother come-down, nowhere near as intense as other ROAs, nor is it's comedown as uncomfortable.
I'd say that the most intense ROA would be intravenous (obviously, merely stating this as a reference point, not a recommendation), with the second-longest duration of any other ROA.
I'm sure others might disagree with this but my experience with hot-rails is just as intense as injecting, but shorter in duration vs intravenous.
Rectal methamphetamine is the second most efficient way of taking methamphetamine, with a 99% absorption rate, very long acting, and the smoothest come-down of any ROA.
Vaporizing it is around 90% absorbed provided that you are a professional when it comes to the act of using a tweak pipe efficiently, but the comedown is too rough for most, leading to compulsive redosing.
Intranasal is around 80% absorbed, but your nasal mucosa rapidly diffuses the meth across the BBB which produces it's effects and has a longer duration and more consistent come-down, but also prone to compulsive redosing.
Last but not least, Oral ROA, 67% absorbed on average, but this number varies wildly. Less intense but extremely long rush period, followed by a steady and consistent comedown. Least prone to compulsive redosing.