Personally, I'm going to disagree with the guys telling you that you shouldn't tow with a compact truck. The new compacts are great trucks, and they're the most capable compacts ever built (most new ones fall in the midsize category with the Dakota). I feel comfortable saying this assuming that you meet the following criteria: 1) locally means with a 5-8 mi. radius 2) you won't be towing often, say more than about 1-2x a month 3) you don't intend to try to haul implements with the tractor and 4) your trailer has tandem brake axles, or you will add brakes to both axles, and add a brake control to the truck if need be. If you meet these criteria, then there is no need in buying a full size if you don't want one.
Compacts have a few advantages and disadvantages in this circumstance vs. a full size. Compacts are typically cheaper to buy, manuever easier (for example parking at wal-mart), have the potential to get a little better mileage, and they are smaller, which may be a factor in whether or not the truck fits in the garage. However, mileage is not always better than on full size trucks (as some other users have mentioned), a compact may not be quite as comfortable for the driver and/or passengers, payload isn't as much as a full size, towing capacity isn't as high, and compacts will typically weigh a good 1/2 T less than a full size (we all know wt. is your friend in a tow vehicle so that the tail can't wag the dog as easily).
Only you know how far and how frequently you will be towing, but I feel confident saying that you can tow a 2305 with a compact truck so long as you tow locally and infrequently. I would guess the loaded trailer wt. to be very close to 5000#, so with tandem electric brake axles and a properly adjusted brake controller, you should be able to safely stop the loaded truck and trailer. Of course, the compact won't tow as well as a full size 1/2 T, which won't tow as well as a 3/4 T, which won't tow as well as a 1 T, which won't tow as well as a class 8 tractor.
As to which of the compact trucks would be best, only you can decide which one appeals most to you after driving them all. My personal pick would be the Nissan Frontier; it is built on a modified Titan frame, has a strong v6, good payload and tow ratings, a well laid out interior, and probably the most enjoyable driving dynamics of any of the small trucks.
I also like the Dakota for a few reasons: 1) it is the largest of the small trucks, so would be the best for towing from a wt. standpoint 2) available v8 for strong torque (but I believe all around you would find either the Nissan or Toyota v6 a better all around engine). However, the Dakota will get poor mileage with a v8, and the power won't come up to the Japanese competition with the v6--so it would probably land itself in last place on my list of the trucks you're comparing.
I think the Ford Ranger is a terrific little truck for the money. If price is the dominant factor in choosing a compact truck, I believe it would move the Ranger into first place. Yes, the Ranger is the oldest design among the trucks you mention, but it is a solid, proven, truck. It is definately the most trucklike (and least carlike) of the compact trucks. However, for the money you would be hard pressed to find a tougher, more durable, and more capable little truck. I wouldn't buy a Ranger with anything other than the 4.0L engine for towing a small tractor.
I have neither looked at, researched, nor driven the Tacoma, so I won't comment on it, other than to say that Toyota builds fine vehicles and the Tacoma should be no different.
Once more, make sure you have functioning brakes on both trailer axles.
