I have enjoyed Mongoose Traveller for some time now, and in the community where I do most of my gaming, it is the easiest edition to bring new players into currently. Considering that Mongoose is presently supporting the edition. Otherwise, I still adore my Classic Traveller books and still reference them often when designing adventures and Game Days. Even after 3 decades of use, they still provide a solid foundation on which to build my campaign.
I run most of my games in the Hard Times Era just following the Rebellion War and before the Virus outbreaks of TNE, which is my shout out to MegaTraveller.
I ran T20 a lot during the years when everyone and their kid sister were playing some variant of the d20 system and couldn't be bothered with the unfamiliar.
I can also endorse Hero Traveller as a door to cross-pollinate all the Star Hero material into Traveller and vice-versa.
Finally, I've been developing a greater respect for T5. It's still a steep learning curve for the uninitiated and a pretty intimidating set of rules. But once my community gets the Mongoose rules into their DNA, upgrading to the greater detail and support in T5 shows just how solid that rules-set is, and how detailed a campaign can really become.