Dolmar = pro quality
Husqvarna 450 = quality name, good saw.
Dolmar definitely built better. But unless you're a pro, the quality difference shouldn't make much of a difference. If you plan to stick with this site and get CAD, (goodluck trying not to get it)... which will most likely end up happening, most issues you have, you'll fix yourself, or at least attempt.
I've had my eye out for a dolmar 421 or makita ea4300 (actually would love to grab the makita ea4300), but I've only ever seen 2 that weren't "buy it now" new. One was non running and still sold for 175.. The other was new and box got beat up in shipping. Sold for 250...
With all that being said, that clearly shows the Dolmar is a very high desired saw, that almost never gets sold after bought. Meaning it's loved... But again, with a one saw plan, if anything acts up on it, you have no saw until shipped back to you.
If I had to pick 1, I'd go dolmar. But, if it was my only saw, and I needed a saw, I'd probably lean 450. Larger cc saw for 1 saw plan, and parts are easier to purchase (Lowes, or eBay always has tons of new and used 450 parts). Again, assuming those 2 are the only options.