I was in the same dilemma when I bought my set. So both of these sets are new with full 1-year LG warranty?
My decision to choose the 9300 over the 9800 came down to luck with price and I did factor in the input lag and the design difference. The way the 9800 sits was a bit too big for my stand so I knew getting that model meant I would have to spend more on a new stand. It wasn't a deal breaker, but it was an extra expense. I have heard some say the 9800 was the better set being the "flagship" model, so the build quality, etc was better than the 9300. When you compare the initial price points the 9300 entered the market around $3500 retail and the 9800 was $9999 I believe. However, user reviews/opinions never really showed any favoritism to either model (other than that LG Vegas guy). Both at their best, performed well and look amazing no doubt.
I also can't say for certain that the 9800 suffered more dead pixel/subpixel issues, but I did read a lot about them in the user threads, but again, may just be bad luck, may be a real issue over time. There was a specific pro review who got a review unit that had about 50 subpixels out which looked bad, but again may be isolated. The 9300 I bought has no dead pixels I can see and I'm not going to search for them, has been performing nicely for the past few weeks

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One thing to remember is if you can pay by AMEX, you can extend your warranty by a year as they give you an extra year, You just need to charge the full amount and I believe it has to be an authorized dealer possibly. I am a bit new to that so thought I'd mention it. I was able to get in on the buydig deal of the 9300 at $1999 so I jumped on it.
At the end of the day I would base your decision on security with warranty vs aesthetics, OLED is a such a new tech, you don't want to save some $ now but pay later if something goes wrong within the next year or so. Either set will blow you away in terms of PQ.
I've also seen the 9300 priced below $2400 shipped from different sources, i would check eBay for reputable dealers, PM Cleveland Plasma on here as well. Seems a user in the OLED Deals thread convinced Buydig to honor the $1999 price as well for the 9300 so YMMV that is a great price though.