If you can save money without sacrificing quality, do so. Be wary of the extra costs a service might tack on and weight them into the equation. Are are they free up to a certain point, say 10 megs, and then they cost extra for extra space. Most service providers won't hide such costs, and will clearly state them in their pricing summaries. When weighing costs be aware of these things.
Some services even charge for support.
Ask yourself how likely it is that your list will ever incur the extra charges. Finally, hosting services have different pricing systems. Services charge by a variety of criteria. Some of the most common include list size and list volume. Some divide categories into discussion lists and announcement lists.