I think STC had more consistent production values than Phase II but I like to integrate the shows (around Chekov's promotion) so I get a mixture of supporting characters. When Phase II is good, it's really good. They both feel like TOS with some TNG sensibilities and story elements.
Specht is a great addition but, to be honest, it would have felt more organic if she had just been Helen Noel. There are definite similarities in their personaliities. I did feel that the final scenes in the final episode were a bit too drawn out for my tastes.
I was glad to see Rand in Phase II but puzzled that fans made her a command officer, despite her being an engineering CPO in TMP. I also felt that not enough of her sass was allowed to shine through. Phase II did an odd thing shoe-horning in Carol when, based on David's age, they must have met much earlier in the timeline.
So in some ways, STC bringing in other, more peripheral, characters and new characters meant that they came with less baggage. They are good support but I think the actors should have had more free reign to seed more personality into the performances.
I am glad that SNW came along and did some justice to Chapel, as both fan shows clearly viewed her as entirely superfluous as part of the ensemble, despite several stories where her bio-research skills would have been of use.
Stringer embodies Nichols physicality really well - she obviously studied the footage - but often looks a bit like a rabbit in the headlights and misses some of Uhura's confidence.
The actors generally do decent, recognisable impressions and any shortcomings are not so much to overshadow one's enjoyment.
Overall, these shows combine to make a great 5th year of the 5year mission.