If we can forget about the hostility for a moment and think about reality and geometry for a minute.
The first question that you need to answer is, "How many SCMS do you want to buy, in your lifetime?"
Cheap today and more capacity / versatility tomorrow?
OK, that is half of the equation. The other half is geometric.
If you are working with 4 inch crown moulding or 4 inch stock you need almost 5¾ inches to cut a 45° bevel. The washer on my 12 inch DeWalt SCMS is about 1 inch in diameter. It should be the same on your particular choice. Assuming that there are no other protrusions from the saw itself you have effectively a 6¼ inch blade. Which really means hold your breath and you might be able to get only 2½ inch deep cut AT 90°. (Specs per HD) The length of the crosscut is limited also to about 8¼ inches at 2¼ depth.
If I were to purchase this saw I would reserve it for cutting aluminum or copper. With an abrasive blade cutting steel would be messy but possible.
Looking at US prices Home Depot and Amazon the DeWalt 779 is $349 and the Bosch GCM 12SD is $593. This DeWalt pricing is usually in the $600 range so the $349 says to me that DeWalt has a new model being planned, probably for the Winter Solstice Holiday (Northern Hemisphere) season. Which also says jump now or their may not be any available later.
I have the older DeWalt SCMS (DW-708 IIRC) and it is a superb saw. The DeWalt is what the pros rave about. The neighbor across the street has a 12" Ridgid from Home Depot. When he did his crown moulding he used my DeWalt for accuracy.
I would say that for only $200 more, get the good one now rather than the cheapie today and a good one next month. You wont be sorry.
The only "hostility" came when someone decided to go for mockery instead of contributing anything actually helpful to the discussion, something that's been happening entirely too much on this forum as of late. Everybody has to say something, even if they don't have anything to say.
As far as "buy once cry once" goes, I agree with that statement. That said, this isn't an issue of buying a cheap POS tool and replacing it down the line, if that were the case I'd just pick up a $50 saw and be done with it. The 7 1/4" saws I'm looking at are all good quality, just smaller than their 10 and 12 inch brethren, and I have no need for larger sizes. The largest thing I would be cutting on a miter saw would be a 2x8, and much more common would be stuff in the 1x4 range, so the extra capacity of a larger saw would be a complete waste of money for my uses. I don't install crown molding, nor do I plan to, and I have a table saw for the fringe cases in my shop where I need to cut larger pieces. Besides, the $200 more that I saw with the smaller saw pays for a lot of materials to build stuff with
I would have a hard time cutting metal and then cutting wood with the same saw, doesn't the metal filings contaminate the wood?
Not if you clean the saw and change blades, which I intend to do anyways. I use my table saw all the time to cut aluminium, never had an issue with a contaminated cut. If you were to add a cutting fluid or coolant to the mix when cutting metal that could cause some issues, but again, clean tools solve that
7 1/4 seems too small. I got a 10", and at the time people told me to go full 12". Several years later, the 10" is fine but I can see their reasoning for the 12". Seven-and-a-quarter, though....
....but obviously you know your needs better than anyone else.
As mentioned above, going for the smaller saw was a thought-out decision. Some shops need the larger capacity saws, mine decidedly doesn't. I don't work with a lot of large, thick pieces, I don't install molding, and I have a table saw I would prefer to use for things like large plywood panels. The 2x8 work envelope of the 7 1/4" blade saws is more than enough capacity for my needs. As an added bonus, a high quality 7 1/4" is a lot cheaper than a high quality 10 inch blade, and cheaper consumables for the same quality is always nice to have