How does the tension and feel of D'Addario EXL165 bass strings compare to EXL170 on a standard 34" four-string bass?

The D’Addario EXL165 bass strings have a slightly heavier gauge than the EXL170, which gives them a bit more tension and a firmer feel under your fingers. This results in a punchier tone and can suit players who like a little more resistance when playing. If you prefer a lighter, more flexible feel, the EXL170 might be a better choice, but if you want a balanced set with a bit more power, the EXL165 is a great option.

Are the D'Addario EXL165 nickel wound bass strings compatible with a 34" scale five-string bass, or are they only for four-string models?

The D'Addario EXL165 nickel wound bass strings are designed for four-string bass guitars with a 34" scale. They are not compatible with five-string basses, as they do not include a low B string needed for five-string models.