China tie rod factory tell some advantages to using sealed tie rod ends versus greased units with grease fittings:

Lower maintenance

Sealed units do not require periodic re-greasing. This saves time and effort. The grease is sealed in permanently and will last the life of the tie rod end.

Protected from environmental damage

The inner workings of the tie rod end are better protected from water, dirt, and other contaminants when sealed. This helps prevent premature wear and corrosion.

Tighter tolerance

The sealing process can help compress the inner parts together, resulting in a tighter fitting and more responsive feel. This may provide slightly better handling and steering feedback.

Less chance of over-greasing

It’s easy to over-grease tie rod ends with grease fittings, which can damage the inner rubber bushings and washers. Sealed units prevent over-greasing since the amount of grease is controlled during manufacturing.

Lower cost over time

While sealed tie rod ends have a slightly higher upfront cost, the savings on avoided re-greasing costs over the lifetime of the tie rod ends often make them cheaper in the total cost of ownership.

Environmentally friendly

Less grease means less wasted product and less mess. Less grease also means less to contaminate the environment should there be any spills or leaks.

Despite these benefits, greased tie rod ends with grease fittings also have some advantages:

Typically lower cost

Basic greased tie rod ends tend to have a lower cost than sealed units, especially if only using them for normal driving needs.

Can re-grease as needed

If preferred, the grease fittings allow re-greasing the tie rod ends when signs of wear or damage appear to extend the life. This allows maximum performance and responsiveness.

Easier customization

The amount of grease can be adjusted based on driving conditions for optimal performance. More grease for high load/high heat, and less for normal driving.

Familiarity

Many drivers are more familiar with greased tie rod ends and prefer them due to experience. Sealed units may be viewed as unfamiliar or untested technology by some.

In the end, it comes down to your specific needs, preferences, driving conditions, and budget. Either greased or sealed tie rod ends can be a good choice.