A 3/4 ton truck is already over kill for your situation, I wouldnt worry about going overkill on the trailer too.  It is rare for someone to wish they had gone smaller/less powerful on anything.........

Sounds like a 3H size GN stock trailer would do a good job for you.

Is the 3/4 truck your daily driver or will it be reserved for work / hauling the trailer only?

I agree with Chadsalt... a 3H, GN with a 4-6' shortwall is a great basic trailer. If you are fairly new to hauling, you might just as well start with a GN. 

I store my tack in the locking DR area and tie the horses to the trailer to tack up. Keeps everything handy. I haul most of the time to trails about 20 minutes away but with the sleeping area, I can also go 3 - 4 hours away for long overnight trips.

No rear tack, but 2 rear doors (easier to handle) I can fit 60-75 small square bales (50-65 pounders) in the trailer and nearly 100 bales of shavings.  I've hauled riding mowers / small tractors in it, and a 2-wheeled cart. Keeps everything I haul clean and dry.

Sometimes I remove the front divider and give my horse 2 slant stalls - especially if he'll be spending time standing on the trailer at shows.

Since you have the truck to pull it, I'd go with a 3 horse gooseneck with a basic 4' shortwall dressing room.   Way more storage, and a place to catch a nap at a show, or camp out of if need be. 

I only have one horse and have a 3 horse trailer and am never sorry to have the extra room, for all the reasons you mentioned. 

The GN is actually easier for your truck to pull, because the hitch is over the rear axle of the truck.

Do you have a short bed truck? then look for a tapered nose. 

Insurance wise, 1 trailer will be cheaper than 2. Less maintenance.

I agree with everyone on the 3 horse GN slant.  It is much easier to haul 1 horse in a 3 horse rig than 3 horses in a 1 horse .  Your truck is definatly enough to handle a 3 horse.

As someone else also pointed out, you might as well learn to haul a 3 horse.  Once you get the hang of it a 3 horse GN is very easy to handle.

Have fun shopping but make sure you look at a lot of trailers.  Everyone is going to have an opinion but make sure you look at quality as well as price.

Trailer on!

Size and budget matters. What do you plan to do with a trailer? Show? Camping? day hauling only? What do you plan to do down the road?

You can get a pretty decent stock type GN...it would suit your needs as far as being able to haul mare/foal ( but if you're not planning to haul many mares/foals then I wouldn't see it as a consideration) Stock types are less expensive,light and easy to clean up but there is no real storage ( there are stock types that have a small DR)

If you are looking to camp or show, then you'll need something with storage and somewhere to sleep/change clothes. A basic DR GN will do. if you want more "comfort" there are nice Living Quarter trailers in all sizes with a variety of features.

There are many different types of rigs but you need to figure out what you'll be using it for then you start narrowing down your choices from there.

I too agree with the answer of a three horse GN with 4' dressing room. You won't quickly out grow it, you will grow into it which is cheaper in the long run. There are many used examples for sale, and new ones at competitive prices.

If you order new, purchase any option available for heavier axles and tires. You may very well, want to later add some LQ embellishments to your trailer, and could over gross the original axles and tires. Many DR trailers have lighter running gear than the LQ trailers of the same lengths.

It's a nice sized trailer, usually around 18' with the 4' dressing room. It's maneuverable and easy to park and tow. A Gn will not give you the balance problems commonly found on the three horse BP, and with more stalls than you will initially need, you will enjoy the extra space, with little penalty of additional weight.

Best of luck   Gard