In my room the XT32+SubEQHT did a better job in smoothing the base frequencies. When I had my AV7005 and AVR-4308, I had a couple of huge dips in the 50 and 70 Hz etc., XT32/SubEQHT was able to improve those by a few dB to the point now from 20 to 100 my room curve look within +/- 2 to 3 dB with 1/6 smoothing. I think I might have posted it in the one of the threads in the subwoofer group.
All that said, it really depends on the individual because a lot of people may not prefer the sound of a flat response. I would say if you are a classical live concert goer, you would prefer flat curve sound or at least find that a good starting point. If you just like the thrill of hearing crystal clear highs, and exaggerating bass, then you may or may not like Audyssey at all, regardless of XT or XT32. Or if you have a near perfect rectangular shaped room Audyssey may not doing anything audible after all.
If say $100 to $150 more means a jump to XT32+SubEQHT then I would say go for it. I know everyone has a budget but in this case you are jumping to a whole different category. The X-4000 brings you not only XT32+SubEQHT but also a beefier amp section, power supply, pre-outs and a 3 year warranty. The 828 (that ranks below quite a few models within the Onkyo AVR product line) offers superior bangs for the dollars, but it is not a Denon that ranks 2nd in their 2013 lineup and is good if you are sure Audyssey MultEQ, 2 year warranty is enough for you to save a couple hundred dollars.
By the way, Audioholics seem to like the X-4000 a lot, read this
http://www.audioholics.com/av-receiver-reviews/denon-avr-x4000-review/conclusion
Question now is, how long will it take you to find the extra $$ and whether you have the patience.