Drive both and see which you like more.
The Gen 1 is heavy, super quiet inside, and sounds like a small diesel truck outside. It's not "fast", but there's a noticeable rush of torque from the 2.0. They are based off the 2LT [gasoline] trim level, so have most of the interior features the Cruze had to offer at the time.
The Gen 2 feels exactly like a gasoline car to me. The engine is quiet and has minimal clatter at idle, there's not 500 lbs of heft over the regular 1.4T models, and there's not as much power/tq as the Gen 1, although it's about the same because of the curb weight. The 9 speed auto is a much, much smoother operator than the Gen 1's Aisin, and interior space is used much better in the Gen 2 IMO.
Neither model really had any glaring reliability issues besides the emissions system junk (Gen 2 is a little better in this respect), and Gen 1 autos tend to get clunkier with age. Gen 1 has a 100k timing belt; Gen 2 uses a chain.
I have both in my fleet of Diesel Cruzes, and probably can't add much to this excellent assessment. jblackburn covered it well.. I would say this, given the 2 choices you presented, I'd not hesitate to go for the Gen 2. Sure, the Gen 1 is $5 cheaper but it also is approaching expensive maintenance, like timing belt. My Gen 1 is at about 78K, so I still have a little time.
Oddly, my Gen 1 had a new DPF in the first week after we bought it, but has been fine ever since, there appears to have been some bad DPFs that got out there. I've thus far had almost no issues with my 2017 auto, only thing that has hit multiple cars, and not isolated to diesels is the door buttons for unlock, I've had 2 replaced, and now have another that is acting up, and they require color matched painted handles to replace, so it's a bit of a hassle, and out of warranty an expense to deal with that, which seems to me is a clear design flaw to have that many fail. On my manual I've had a failed flywheel, but you are not looking at any manual transmission cars.. I love the manual, but I would caution anyone looking at one to be aware of the dual mass flywheel impending doom.
Also, seeing as you are CA and emissions testing, the Gen 2 system is much more reliable than the Gen 1 for emissions stuff, and it shares considerable share of parts with the higher numbers produced 2.8 Duramax diesel, so going forward parts and maintenance will be less of a concern. The Gen 1 was a very low numbers deal, it's engine and emissions system, even the programming is unique, as are many of the parts.. so that should not be ignored.