If a recently built, high quality, older technology bike could be found I expect it would be reliable. However, I don't think they would stay in business long (although Ural seems to keep going) with the improvements from modern technology applied to increase performance and reduce maintenance.
Older technology requires more maintenance. One of the main 'selling points' of modern technology, aside from little deterioration and neglect, is the reduced adjustments and tinkering required accompanied with improved performance. Hence, why people want modern.
Taking an older motorcycle on a longer trip can be an adventure in itself. Taking a new motorcycle on the same trip makes for a different journey. But, if the trip is really all about the journey and not whether the destination is reached, then it's up to the rider to decide what is best. But, to answer the original question, either technology will work and can be reliable but finding older technology in good condition is not easy.