I have a John Deere gasoline Weed eater. It came with a brush blade and a string feed hub.
It ate more string than weeds, so I put on a universal string holder that uses short segments of very hard, thick cord. That worked much better, but still ate a lot of those string refills.
I have since switched to a new solid plastic 3 blade unit. It has three pivoting plastic/nylon blades with thin serrated metal blades sandwiched in the plastic so that only the edges of the metal blades stick out about 1/8 inch. I have had those blades on it for over 4 years now and they work as good as the day I put them on! I don't remember the brand or where I got them (I think it was at Home Depot) and the kit was about $15-$20. I think it came with a lifetime guarantee on the blades...if they ever break, they will replace them free.
The problem I found with many small, cheap rechargeable weed wackers is that they don't have the power to spin the metal or plastic blades. They can spin them fine until they blade meets some resistance, like thick grass or weeds and then they tend to stall out and you have to lift the weed wacker up and let it regain it's speed and momentum before attacking the weed again :angry: That's worse than having to constantly bump it on the ground to feed more line, or stopping to change or refill the spool.
...Rich