What is the coinsurance percentage and maximum out of pocket? It sounds like the HDHP is probably best, particularly if the HSA contribution is only for the HDHP (which it probably is, as otherwise it'd be a FSA, but sometimes companies are lax about the terminology).
Here are my work options and the comparison I did:
Regular:
$5,700 annually
$600/person, $1,200/family deductible
$3,400/person, $6,800 family out of pocket limit
$25 copay (mostly)
10% coinsurance (mostly)
HDHP:
$4,900 annually
$1,350/person, $2,700/family deductible
$4,300/person, $8,600 family out of pocket limit
No copay, but 20% coinsurance applies to visits as well as labs/imaging/facilites/etc.
One member of my family has a chronic health condition and typically incurs about $20,000 of expenses. Let's assume for the sake of math that the other three are perfectly healthy and accident-free.
Regular:
$5,700 premium
$600 deductible
$1,500 copays (estimating about 5 visits/month)
$1,300 coinsurance (10% on $15,000 in outpatient visits/labs/imaging, but we've hit the per person cap)
$9,100 total health spending, of which $8,250 is pretax (premiums and $2,550 FSA limit)
HDHP:
$4,900 premium
$1,350 deductible
$2,950 (20% coinsurance on $20,000 of expenses, but we've hit the per person cap again)
$9,200 total health spending, all of which would be pretax as I'd put the max into the HSA.
Tax benefits give the edge to the HDHP, but chances are high that one of the other 3 members of my family would need a non-preventative office visit at some point, which would be $25 with the regular plan and $100+ with the HDHP.