When were nuclear subs faster than conventional? Nuclear submarines are significantly slower because acoustic restrictions disallow generators to operate at full capacity.
The majority of countries still favor conventional because it's faster, safer, more quiet, easier to design, economical, and politically viable.
Nuclear subs are much larger in volume due to the minimum space reactors and filtering systems occupy. Thus, it is more cost effective to lower the hull-to-reactor ratio by enlarging the entire design for more arsenal. These attack subs are significantly larger and much louder on the move. That is why most countries focus on nuclear ballistic submarines where mobility is not a priority. Nuclear attack subs are falling out of favor worldwide due to export and operational restrictions.