As with everything, it depends what you want, and what your definition of strong is. Do you like procedures? Is there a certain aspect of family medicine you want more of? Is this a stepping stone for operational billet? Are you worried about board pass rates?
People often pick these things based on location. If you don't like where you are, then you probably won't have a good time. But, if location isn't a deciding factor for you:
In terms of size Pendleton and Jax are the biggest programs with typically 13 in each class, while Lejeune has about 9 and Belvoir has 5 navy but is the largest program overall. All of these programs are at places where there aren't competeing residencies; however, Pendleton and Belvoir will roate at the larger MTFs nearby, and Jax has a lot of out rotations in the community. So it depends if you want more colleagues to coloaborate with vs compete with (for things like procedures).
Each place also has different focuses and populations. Pendleton loves sports medicine, while Lejeune likes OB more, as a couple of examples.
Due to the triservice program, Belvoir has more people go GMO after first year, dpending if you want that, or are looking to avoid that.
Jax probably does the most rotations with civillian hospitals nearby, if you want to see civillian medicine more, or are planning on getting out soon for that.
If you are looking for inpatient experience, probably Lejeune gives you te best opportunity.
The possible list of pros/cons is large, depending what your goals are.