Having been on both sides of both fences...
...my experience is that the SME's think that good enough is good enough and the big corporates want the best of the best, so that they can be the best.
I once specced up a system for one of the largest firms of its type in the world and it was a paper- based system. They were horrified and wanted a computer system. When I produced the justification for the design, they instituted the paper system the next day and, as far as I know, they are still using it - I demonstrated "necessary and sufficient" to them.
When running a SME, I specced up Sage Line 50 (back in the day) for the accounts and it had errors in it (the VAT calculation was erroneous if you put the figures in one way and correct if I used another part of the system). It became so frustrating that I ended up using Excel for all of it (an old banker's trick), which worked very well. Egg on my face there for an over engineered solution spec.
As a corporate buyer, I became wise to IT salespeople and used to send them out for coffee, whilst I talked to the techie. That saved an awful lot of money because salespeople are basically bullshitters (my non-techie division director nearly fell off his chair when a salesman for a big data processor talked about "massaging the data" in one meeting, for example) and it's easy to tell if a techie knows their stuff - which they generally did. However, the general view, in my experience, is that corporates throw money at things to maintain (or gain) a "competitive advantage". Actually, I wanted that particular product precisely because I could massage the data but that was too much information for my boss. Nevertheless I got it in on a practical basis that ensured his arse was covered and massage was not mentioned in my guff.
Running a SME, I wouldn't buy anything unless I had to or I could realise an immediate uplift in the bottom line.
Early on in my business career, I came across a phrase that seems to portray the difference in thinking between a SME and a large corporate with great accuracy: "The fox runs for his life, the hound runs for his lunch".
I see the same phenomenon with fish tanks - a big fish tank is less susceptible to fluctuations in composition than a small one. I think that this is the fundamental difference between the two extremes. Microsoft is reputed to have enough money in the bank to pay everything for six months if it didn't bring in any money at all. What SME has that amount of "give" in their business model?
Another factor that springs to mind is that SME owners generally have an intuitive feel for the state of their businesses at any given time, whereas corporate types have to look it up on a system somewhere. That's a big difference in awareness.
Then, there's sales and marketing. The perception of sales and marketing at the corporate level is nowhere near the perception of sales and marketing at the SME level. SME's just don't seem to understand a sales led organisation, they only seem to understand a demand led organisation. This is simply because SME's don't have the marketing budget of the corporates.
Finally, there's debt led expansion. Since the '90s business schools have taught that debt led expansion is another way to achieve a competitive advantage. For a SME, debt is the devil incarnate and it really does keep small business owners up at night.
I can't really fault either mentality as an approach to succeeding in capitalism, I think that, if we are to have a world that is an ecosystem of big corporates and SME's then we need to understand and see the value n both perspectives. Ugh, I'm sounding like a Rand Corporation think tank. Time to go.
In conclusion, there is an obvious discontinuity between the thinking of the small business owner who earns money to put a roof over their head and food on the table and the corporate type who has a salary coming in every month.
The fox runs for his life, the hound runs for his lunch