Hi,
This is very much an issue of personal preference and, perhaps, driving style.
The modern 5-speeds are pretty widely available and easily adapted. They will make highway driving more pleasant.
For more "sprited" driving on twisty, windy roads the overdrive is hard to beat since it effectively gives a close ratio 6- or 7-speed gearbox (depends upon model and setup... on the earlier cars they OD was usable on 2nd gear, it was not on the later cars. All offered OD on 3rd & 4th. It is possible to set up 2nd gear OD on the later cars, though, if wished.)
With the various possible 5-speeds there are some gearing choices to make. With the OD, it can be set up to provide 22.5, 25 or 28% reduction.
Some 5-speeds might weigh in a little less than the TR gearbox combined with OD (approx. 125 lbs). If any vintage racing is planned with the car, the OD adds significant weight, but a modern 5-speed might be prohibited by the sanctioning organization.
Happy shopping!