I got that question this week, and I decided it wasn't a quick answer so I would respond with this post.
There are Pros and Cons to Blanketing your horse:
Your horse will stay clean. This counts as like ten pros in my book.
Your horse will not grow as much winter hair, so he will dry quicker and be easier to cool down.
Your horse will be comfortable in severely cold weather.
If you make the choice to blanket your horse, you will need to pay close attention to the weather. If its going to get warm, he will need it taken off. You don't want him to sweat under his blanket. That can lead to some severe health risks.
There are so many options,
Turn out Rugs
Turn out sheets
I would only suggest the hoods if you are going to be showing. Then you will need to implement a light program as well as blanket program. Not only does the temperature affect your horses hair coat, so does light. I always put my lights on a timer. They came on at 7:00 AM and stayed on until 10:00 PM.
For stabled horses, I like the Big D blankets.
Severe Cold Weather
They seem to fit my Quarter Horses really well. Halter horses and Riding Horses. I never had any problems with Big D Blankets or Sheets.
For the horses that spend a lot of time out in the pasture, I like the Rambo Turnout Rugs.
They are real sturdy and warm.
They also make a lite turnout rug for less sever weather.
Another concern of mine with blankets is that if your horse is outside and gets wet, his blanket gets wet (especially if it is not waterproof), and then when you bring him inside, if you don't change his blanket he can get rain rot.
You also don't want to have your horse blanketed, and then have short hair, he gets his blanket wet, and you leave him "naked" overnight to freeze. So again, it's wise to have more than one blanket.
It is really nice to just pull off the rug and have a relatively clean horse. But you will need to make sure that it comes off on warm days, and it goes back on for the cold.
Leg straps are a must. If you don't have them, your blanket will simply not stay put!
There is no absolute right or wrong answer, the real answer depends on you and your situation. I can't give you the answer, I can only help you make an informed decision.
*State Line Tack is an affiliate of Improving Communication Between Horse and Rider.