My tape is Horseguard and I like it a lot. I would also trust Ramm to make a good fence.
In general, with fencing, the cheapest option is cheaper for a reason that will eventually make you sad. Electric fence depends on the gauge of the conductors to propagate the charge down the fence. People who sell electric febnce and want to make it cheaper will use metal that is less conductive and less of it both to save on the metal and on the shipping weight. The plastic elements may not hold up as well to UV light.
The reason to use a solar charger is if your fence is not near a source of electricity or if your area sees frequent power outages. The reason not to use a solar charger is that they’re more expensive per joule and they don’t generally have as much shock as an AC charger.
http://www.premier1suppplies.com is a good catalog to learn about the limitations and benefits of solar chargers. They’re not the only quality vendor but they have wonderful diagrams to explain some of the different issues and tradeoffs.
I’m not a fan of the plastic step-in posts. I find that the plastic degrades pretty rapidly and they’re also absurdly short for horses. For temporary use they’re ok. As an alternative, I’d suggest HorseGuard’s fiberglass temporary posts. Those are a little harder to drive but they are taller and last a long time, and they won’t crumble in your hands when you move them.
One of the questions is how aggressive these ponies are and how much they’ll want to be on the other side of the fence. You want to be sure there’s a conductor at nose level, because that’s where they will learn the fence hurts. If they touch it with their necks or manes first they can duck through the fence pretty easily, and the shock will send them forward through instead of back inside.
Another question for you is how much trouble you’ll have with weeds growing into the fence (that will eat your charge in a hurry) and also how moist your soil is. If your soil is really dry in summer, the fence will be less effective, because it depends on moisture in the soil as a conductor. In this case, the bipolar fences are worth considering.
Electric fence is a mental barrier rather than a physical one, so if the other side of the fence is especially bad (busy road, ponies are unattended most of the time, etc) I would recommend having two layers of fence that they have to get through before you have a problem.