Up to a point where it gets too heavy more power is always better. Both units are fine on weight. For some uses you would want more power than the 230 perhaps. You just wind up revving it less and it may last longer.
If you already have an identical unit I find buying multiples of the same unit helps down the line as you can use old trimmers for parts on newer ones. I have a graveyard of old Echo trimmers in the shop. From recoil mechanisms to prime bulbs or entire carburators, you can save a little on parts.
Be sure to use the proper octane fuel with echos, my newer ones have been very sensitive to that.