I have a battery powered Makita and it works as good as the lower priced gas chainsaws. It has a 14 inch bar on it, so it will cut real wood.
The advantage to battery is - no pull starting, no carb, no air filter, no mixed gas/oil, no spark plug, quieter and smoother. Charge the batteries, push the button and go.
The disadvantages? Really two: The batteries have a limited charge - mine will go 20-30 minutes on a set of batteries. I have a couple of sets, but that's less than an hour of cutting. If you need to cut for hours at a time they are impractical. Second, Cost. My battery powered chainsaw is the same size and a little less powerful than my Husqvarna 120 Mark III - which is their lowest price model, right now $220 on Amazon. My Makita runs $350 without batteries and $450 with a set of batteries and a charger. That's expensive for a low-end saw.
I suppose also the longevity of the tool might be in question because of the batteries. Battery tools tend to die long before they are worn out because the batteries themselves become obsolete.
For trimming and cleanup work battery saws are great. For heavy stuff it's still a gas world.