I would favor the larger place for an early career person and the smaller one for someone in mid-late career. Since the two institutions are of similar rank/standing it would imply that the pressure for research at the two places is similar, unlike the situation where the smaller one were a liberal arts college with lesser research requirements.
The advantage of the larger place for the earlier career is the fact that there are greater, closer, collaboration opportunities and more opportunity to share ideas through seminars and such. You also say that the larger place is active in bringing in visitors. Even the coffee lounge at a large university is a very fruitful place to spend time.
This might be different if the smaller place is rich in travel money and provides travel funds for conferences and such. It might also be different if it is located in a place where contact with many local businesses/corporations, with possible consulting or collaboration possible.
But, to build a research focused career you need contact with a lot of people and it needs to be fairly intense in many cases to be fruitful. More local people with similar interests is a plus.
For an older, established, academic this is less important as they have likely already developed that circle of professional acquaintances and collaborators that the new kid on the block doesn't yet have.
This might be different if the person is interested in multi-disciplinary work within the field, crossing sub-field boundaries. That might be equally available at the smaller place.
Don't ignore place in your decision. Small towns and big city living is quite different, both in cost and style. But some big universities are located in small towns and vice-versa. You want a comfortable life style, not just a comfortable work environment.