There is a lot of information to digest if you are coming to this not knowing anything about the different services. The Iridium and Starlink are very different, and the answer isn't that one is better than the other, it is that they are very different.
Starlink has a fairly large antenna, and depending on which you choose, might be quite large. Starlink uses quite a lot of
power, and many
boats struggle with that. You will need a lot of
solar, or a
generator, to run starlink. If you are just making it now with your
power needs, you won't be close to being able to run Starlink. Starlink is also not a means for
emergency communication. You can't take it with you in a
liferaft. And in many emergencies, if you lose power, or take a large wave that hits the antenna, Starlink is done fore.
Iridium (there is also the Go! which is cheaper than the Exec) is extremely slow. It has been used for years by many sailors for weather and text only
email, and works fine for those. Most
boats find a benefit for an external antenna, but it isn't always required because there is an internal antenna. The external antenna is very small, like a
GPS antenna. It also works for voice by tethering a
cell phone to it. It has an internal
battery and can be taken with you in a
liferaft. But it is pretty much useless for any other
Internet uses outside of text only emails and weather. The exec is much faster than the go!, but still don't expect to use it for anything other than weather or email. I'm not sure I would put out the
money for an exec over a go!
Starlink is great at Internet. For surfing the web, streaming movies, social media all work as well as if you were on land. For what you get, compared to Iridium or other high speed Internet services on boats, it is really
cheap. But, if you get Starlink, you really need to also get an inreach (which is also Iridium btw) for
emergency coms. Some sailors have both a Starlink and a Go!, so when the Starlink goes out in an emergency, they have the Go! to fall back on.
Then there is the question of what plan to get. Starlink has 2 dishes to chose from, a smaller rectangular dish that will auto tilt to get the best signal, and a larger antenna that is flat and doesn't move. Both are awkwardly large to mount. The larger one uses even more power than the smaller one. Officially, the smaller one is not allowed to be used on boats or in motion, but it works fine. For now, as Starlink has a
history of changing TOS or starting to enforce TOS that they let slide for awhile.
Starlink has a "roam" plan, a "motion" plan, and a "priority" add on. The "priority" add-on is required for ocean use, and is $2 per GB.
For the Iridium Go! it is more simple, get the unlimited plan.