Ditto BayHawk, Alexandra and DownYonder’s prior posts about “stallion behavior” and “temperament”. I think many novices to the stallion psyche often get the two mixed up.
That said, to answer the OP’s question, the decision to keep a colt intact can (and should) often be based upon what the inspection jury has to say when he is first presented. They’ve seen thousands of colts, so use their experience to help you with that decision. Then, you’ll find out at a licensing whether their assessment pans out or not.
Be prepared to have some deep pockets to get through the process of owning, training, semen evaluation costs and marketing the horse (as well as housing modifications needed to keep a stallion and other horses safe and content).
When Argosy was sold out of the Elite Foal Auction in Verden, the jury suggested to the buyer that he not be gelded – that he MIGHT be a stallion prospect. That is why he was not gelded. I bought him at 2 1/2 as a PROSPECT. He failed the Hanoverian licensing due to a big fat ankle from having injured his leg some weeks before. 3 mos. later he was licensed by the GOV. Though he never made it to the 100 DT so long ago when it was very difficult (and with problems between the Olds.) and his license eventually expired, he has been sought after for hunter/jumper sport prospects.
And interestingly, though he is no longer licensed, he has an approved son with Old/NA from his very first foal crop.
There is a lot of time and money and management involved with stallions – beyond the “stallion behavior” vs. “temperament” issue.
I’d look at the complications a stallion can bring to your life, your farm set up/management and your pocketbook first. If you can’t accomodate, happily, all of that then what he’s like is a moot point. And, most of all rely on inspectors who are very experienced in picking colts that actually DO wind up being stallions.
It can be quite a journey, and a fun one, but frought with challenges that is not for everyone…
Good luck!