5.9L Cummins (IS/ISBC):
* Pros: Generally known for its simplicity, reliability (especially the earlier versions), and ease of maintenance. Many aftermarket parts are available, making modifications and repairs relatively straightforward. Strong community support and readily available knowledge base. Usually cheaper to buy.
* Cons: Less powerful than the 6.7L. Less fuel-efficient. Older technology, lacking some features found in the 6.7L (like emissions controls – although this can be a pro for some). Can be prone to specific issues depending on the year and modifications.
6.7L Cummins (ISG):
* Pros: Significantly more powerful and torquey than the 5.9L. Generally more fuel-efficient (though real-world results can vary). More advanced technology including better emissions controls and electronic features. Typically comes with more modern conveniences in newer trucks.
* Cons: More complex mechanically, making maintenance potentially more expensive and difficult for a novice. More expensive to repair, and parts can be more costly. More susceptible to issues with its electronic systems. Can be less readily tunable compared to the 5.9L, though this is changing.
In short:
* Choose the 5.9L if: You prioritize simplicity, reliability, ease of maintenance, affordability, and have a smaller budget. You're comfortable working on the engine yourself. You're not concerned with the latest technology.
* Choose the 6.7L if: You need maximum power and torque, prefer better fuel economy, and want the latest features and technology. You're willing to pay more for the higher initial cost and potential repair expenses.
Ultimately, the "better" engine is subjective and depends on your individual needs and preferences. Consider your budget, mechanical skills, and how you intend to use the truck before making a decision.
