I use both methods but for different reasons. I use the portable electric corrals to let mine graze and just to relax and roll after a long ride. I can fence about a quarter acre in 45 minutes or so. This works pretty well when you have a small herd that you can keep an eye on.

If I am leaving them overnight OR I have to leave one or more in camp while others get to leave for a day ride then I don't trust the corrals. The animals get highlined in these situations. I try to find an area with a durable rocky surface and rake the area of leaves and pine cones (rake back over after you take down the highline). I find trees at least 7 inches in diameter or tie between two trailers. Some youngsters and mules will paw on a highline, so it helps if their bellys are FULL and they are close to their buddies.

Well I have listed this in the "camping with horses" thread but I have created a webpage demonstrating highline construction. I just started this webpage (my first one), so I would appreciate some feedback...

http://pkrigerjr.tripod.com/highline.html

I have high lined all my horses, from yearlings to late 20 year olds for the first time and never had any problems. One of mine gets bit by an idiot bug and will pull back and break lead ropes and stuff (This only happens once every year or 2 now) when he is tied to something solid. He used to do this constantly when we first got him about 5 years ago. Funny thing was, is that when he was on a high line, he would never do this. I used to corral mine with hot wire until 1 time I forgot my fence charger. This same gelding got out went around to all the campgrounds all night visiting while his buddy stayed put. Needless to say, we had no choice but to high line for the next 3 days. Never again will I go back to the corral. It is much easier and faster to put up and take down a high line. It also takes up less room. We all know how we love extra storage space in our trailers :) It's the first thing that goes up and the last thing that comes down.

Pros & Cons....

I was at an endurance ride last year and if you ever go to one, you will see, everyone uses electric corrals or the small pvc fence corrals. A horse got a little upset and ran out of his corral and through someone elses corral leaving four horses loose. It didn't take but a few seconds to catch the horses. I think most of them are really used to all the commotion of an endurance event, so they just stood around waiting to be caught. No one was hurt, etc.. The good thing was, none of the horses were hurt. The bad thing was, the horses were free to run off.

Hope this helps...

I like my portable electric corral too, but I use it for entirely different reasons: it is for grazing, and some relaxing time after a ride ( my mules LOVE to roll!). BUT I don't trust it for leaving animals in camp if I am leaving for a day ride and only rarely for an overnight stay. That's where the highline shines...as a safe, secure method of stock containment.

Oh and just in case you live in an area without "HUGE" trees LOL...You can setup a nice highline between two horse trailers. If you are sleeping in the trailers, you may experience a little trailer rocking if your stock doesn't stand quiety. 

I pack a portable electric fence into the back country with me. We will put the horses out in it during the daylight.  At night we bring them in and highline them. If they have a full gut from grazing the are usually pretty content to stand tied to the highline.

At CTR & Endurance rides I use the HiTie system and tie to the trailer. It gives the horses more room than just tying to the trailer side and the fiberglass rods asorb A LOT of the horse movements so I don't feel him tugging on his lead all night while I'm trying to sleep.

I have not hauled panels, mainly because I didn't want to fasten them to the side of my nice trailer. The HiTie gives almost as much movement to the horse and sets up in 30 seconds.

I have a 21-year old TN Walking horse.  I got her about 2 years ago.  I have high-lined her at some trail rides.  The only thing that I don't like about that is not-knowing what might happen during the night & then have to go find a horse that has broken free or gotten caught in the highline.  Back in April, there was a large organized ride down at Ward, SC that had 465 horses.  I noticed that at least 5+ horses broke loose during the weekend & had to be caught.  I don't think any of them were hurt or anything.  While at this ride I saw some smaller portable corral panels.  They are 4'3" high & 6' long.  I have a steel Bee 2 horse slant - stock combo trailer that weighs 2,500 lbs.  Since I only haul one horse, I have the panels standing on their end pointing to the ceiling of the trailer with the 6' section going up toward the ceiling.  I have them tied in with a motorcycle tie strap.  I like them because the fit inside my trailer.  I would be afraid to have panels on the outside of my trailer.  Not only because it would damage the trailer, I would not want to have the chance of them coming off of the trailer while hauling.  The panels are 1' square tubing so they are strong.  Even though they are steel, they do not weight much & anyone can set them up in just a few minutes.  The guy has other sizes & could probably make what ever size you needed.  Mine have 4 crossbars.  I wish that I had them remove one of the bars & evenly space three crossbars so that a horse would have less of a chance of slipping a leg between the bars.  Here is the website that has the panels like I bought.  He is located in Saluda, SC.  The panels that I have are like the ones in the 4th & 5th picture on his main web page.  If you are interested, call the owner Russell Durst or his son Clint Durst.  They will be happy to talk with you about their panels.  They can paint them in whatever color you want.  Also, they can have them powder coated to help prevent them rusting.  If you have room to carry them, I would suggest some small corral panels.  I can sleep better at night while camping knowing that my horse can lay down & roll if she wants to without having her head tied up on the highline.  She will sleep better & be better rested for the ride the next day.  Also I feel better about her not getting loose during the night while I have her in these panels.

http://www.carolinacorral.com/corrals.htm