I'd say flooded lead acid is probably the best bang for the buck. If buying new, I hear golf cart batteries are pretty good. AGM and Gel are generally more expensive per amp hour, and cannot as easily be maintained. Good old school flooded you can open the caps and check electrolyte levels and add more distilled water as needed. VRLA, Gel, AGM etc DO vent sometimes, except when they do, you can't easily refill them. They tend to have a shorter life span because of this.
If you setup a good flooded acid battery bank and take good care of it, it should last 10+ years. The telco ones tend to last 20+ years. They do lose charge capacity over time but if you oversize from the get go and avoid discharging them too much they will last longer.
They are also simpler to charge, because you can float charge them while the load is also connected. Lithium ion is probably going to get to a point where it will be cheaper than lead acid and their higher density means more capacity per square foot of space, but they are much more complex to charge because they need to be balance charged and at very specific voltage/current. This gets complex if you are also drawing energy from them while they are also being charged, such as a renewable energy setup.