Understandable. Honestly, if I had been in a position to make your choice I probably would've gone for the Temporal Light Cruiser too. (I mean, the Atlas maybe has more deeps, but the Connie's a Connie....)
I forgot to mention it before, but one of my other characters is a TOS-styled Klingon (I wish that was a real separate subfaction, but that's a different discussion) who flies a D7 Temporal Battlecruiser. It doesn't "feel" as powerful as my other character's Atlas, but that could be down to the fact that the Klingon is a newer/lower-priority alt with less optimization and/or other differences in the build, not necessarily the differences between the ships themselves.
Speaking of which...
(Also, if anyone wants to comment on how good their equivalents are, I would be happy to replace a Constitution-class with a (captured) D7 or T’Liss.)
The D7 is IMO a straight upgrade from the Connie with the addition of the cloak, although I guess YMMV depending on how you feel about replacing the universal/command seat with universal/intelligence). However, it's not a Connie, so I'd say skip it for space barbie reasons, unless used on a KDF character after the TOS FED one has already been squared away.
The T'Liss is even more mechanically interesting, since it's got singularity core abilities (but no cruiser commands), an experimental weapon (while keeping the 5 forward-facing slots!), and adjusts the seating to have cmdr tactical/temporal instead of cmdr engineering/temporal (which is a double-edged sword because you gain the possibility of CSV/CRF III, but are stuck with 3 eng-only slots where you could've loaded up with temporal abilities before) and universal/pilot. That's all pretty neat, but again it's still not a Connie, so I'd say save it for a Romulan alt later.
Well, that's optimistic.
Meanwhile, I'm over here imagining them summarily executing litterbugs.