Wow...must be the only one without a hangover this a.m. Just kidding.
Plinker Plus? Is that an Olympic Arms model? Nothing against Olympic Arms or any of the other so-called 'non-top-shelf makers out there'. Not really familiar with it, other than their first attempt at an inexpensive "plinker" model that had a few bad traits. The original was made from a CAST receiver versus Forged. That in itself isn't necessarily a bad thing, unless of course you are going to be seriously using your firearm, putting alot of rounds through it (like during manuevers, operations, or a firearms training class), or that particular 'casting' wasn't done correctly. Most of the negatives I have seen or heard of involved the latter, where the casting was flawed by improper pouring, temperatures, foreign material, etc. and the casting ends up in pieces - usually while in use All kidding aside, that kind of failure could result in serious injury to the user or innocent bystanders, even death.
By now, I would think (and hope) that those kinds of incidents and failures have been addressed and corrected, so it may not be an issue at all. Maybe...
The Del-ton kit you mentioned would be a very good way to go, even if only for the fact that you would be putting it together YOURSELF. This is something I highly recommend to folks, in that it teaches you alot more about your AR than buying one across the counter. The process is simple, well documented, there are several folks on here that have done it - some multiple times, and lots of advice and assistance is available - the biggest PLUS being, if it ever breaks, YOU yourself can fix it.
Now the downside....Del-ton, last I heard, is backed up with orders, some up to 6 months out. So if it is something you were thinking of picking up soon, you may be disappointed and have to wait like so many thousands of others.
Price wise, I think both options would be very close in price. Value wise, if you ever decided to sell it, I think the Del-ton kit, even if you put it together yourself, would be the easier sell, based on the quality of the parts. But then again, that's only my .02. Your mileage may vary depending on whose opinions you end up going with.
Good luck on your choice and keep us informed.
and HAPPY NEW YEAR, too