I've been facing a similar dilemna but I think the answer depends on which metals you are trying to match. Empress moderns (Cold War, Ultra Modern) are 32mm in reality, as are Underfire Miniatures (same sculptor). So if you are looking to match with 3D prints those suspect 32mm is the better bet. It's basically what 1/50 scale models are scaled for. I'd put the Gringo 40 Vietnam range in this category as they are significantly larger than the Empress Vietnam range
Empress Vietnam are the more typical 28mm as are Eureka* for the most part. TAG are beefier although not necessarily taller.
*Kriegspiel Miniatures also manufactured by Eureka are more 25-27mm. The Vietnam range by the same scultor, the late Mike Broadbent, are a little taller but still on average shorter than either the Kosta Heristanidis sculpted Eureka moderns or the Empress Vietnam range. That saidm with appropriate basing adjustments, most can be made to fit with Empress.