Now this is a serious question, and not a just "I don't want to spend the money" response. Although I really don't want to spend the money. :)
The 100 watt runs around $75-$90, and I understand I'd also need a controller, about another $25, I think. A 10 watt maintainer is around $25-$30, with no need for a controller as long as it has the blocking diode, I think.
Now what do I get for that extra $100? Bear in mind I'm just thinking of keeping the battery charged in the toyhauler over the winter. When we travel we have a generator, which is rarely used, and stay at full hook ups almost invariably. But I am open to suggestions that can be used to justify the extra expenditure.