First let me say welcome
It sounds like your thinking is somewhat inline with my own when I was first looking into J knives, and that is just what would I be getting for the extra hundred, or hundreds spent on more expensive knives. I will admit up front I can be tough as a buyer and look for the most value often, but like most others can really enjoy a purchase of something exotic or high quality etc no matter the cost.
So how to tell exactly what you will be getting for the extra money spent though a great thing to know is really hard to figure out without actually owning or using both so you can make your own comparison. Sure some of the more experienced members can share their knowledge (and again thanks to all for doing so) but it still is a tough task at hand when your new to this type of product, and even more so if your new to cooking or knife skills etc
Figuring this out drove me nuts (and I am sure most those here helping me lol)
Another issue is what you will be comparing your next knife to, and what skills you have etc as this will play into just how satisfied you will be also.
I do fully agree with BDL on his recommendation of the FKM and DP series and that they are very likely two of the best entry level J knives (based on my experience with these brands, and previous german brands).
I have owned a Fujiwara FKM 240 Gyuto for about ten months now, and though I can not compare first hand to the MAC or any of the other more costly brands I can tell you that IMHO it is a pleasure to use, easy to sharpen, feels good in your hand (especially pinch grip), seems well balanced, can get very sharp with little effort and hold that sharpness for a good while (much sharper than any Henckels I have owned including those that retailed for much more $ and will hold that edge so much longer it is a joke).
Now that does not mean it is perfect and I am not sure anything ever is, but dollar for dollar it is going to be hard to beat.
The Tojiro DP is one of the others I have and also like very much. They are a bit different in design, material and feel than the FKM and the F&F were not as good though close. I think the biggest differences are the handles, the blade steel used, how they sharpen, and edge retention.
Since the DP uses a harder steel (vg10) it is a little tougher to sharpen, but also holds the edge a little longer. Though they get very sharp (maybe even a tad sharper than the FKM) they do not feel as nimble as the FKM does, but to be honest this is really close and splitting hairs, but there is a difference.
I think anyone new to this will be very happy with either of these, and it is a very inexpensive (less than any brand name German made, and not much more than clearance or seconds too) way to get started into the world of J knives, and even more importantly if your on a tight budget will leave plenty of cash for buying at least one stone if not more.
I almost failed to mention that picking your stones will be just as much fun and maybe even a bit more confusing than the knives your going to be sharpening on them. Though I would not recommend it for everyone I ended up being a bit too frugal and originally went with a single stone that would do the job, but was in between popular grits (a shapton 2k glass stone) and my set will be growing around it soon rather than with it. My original thoughts on a combo stone may also have not been great long term, but would have been better short term (king 1k 6k combo etc) since it would have had better coverage of grits.
It is just luck that the 2k has worked out with a little extra time when needed, and as an added plus has been great with my non kitchen knives as well. So if you have the funds avail for more than one you should be ok, and it is easy to add to later if you chose quality ones now, but if money is tight I do not see anything wrong with a combo or even just one glass stone if your shy for gouging into the stone etc. I am sure the others here with more experience with different stones can steer you in the right direction.
Back to the higher cost knife question.
Since I currently deciding on the next addition to my collection I can add a little more to this. When I first started I was totally about value and getting into the swing of this before spending any serious cash, but I was and still am insanely curious as to just what does one get for the extra money. Honestly I can not wait to be able to make a first hand comparison between these sub $100 knives (my Tojiro petty was under $30 at the time I got wow) and those costing so much more.
Wish I had this info for you now, but from what I have read in various reviews and informed replies it seems that as much as I expect to be impressed I should not expect to be as much as I was with the entry level compared to my previous Henckels Pro S. Just look at how BDL deals with the difference from the Mac above, and it seems as if the changes become less extreme, but obviously there are differences as he does produce a list of them every time lol
If you really want better or more in depth information I think you will need to let us know what your using now, what your experience is, and also budget as it gets more interesting once you get into the $150+ price range as there are so many more to compare.
Also if you like read some on my own voyage through this here http://www.cheftalk.com/t/63213/tojiro-dp-f-809-240mm-gyuto-a-good-budget-entry-level-intro-to-japanese-knives/90#post_363860