I wanted a license for Mathematica that allows commercial use (as a single user). After doing an awful lot of reading at the Wolfram website, I decided to purchase the Developer license for Wolfram Development Platform because it is around 1/10 the price of the comparable Standard Edition Mathematica.
As far as I can tell, the Wolfram Desktop that is included with the Developer (and higher) licenses for Wolfram Development Platform, is essentially the same Mathematica that I've used for 20 years.
I am interested to know what capability differences there are (if any). In particular, does Standard Edition Mathematica have any capabilities that are missing in the Wolfram Desktop that comes with the Wolfram Development Platform?
By getting a free trial of Mathematica 12.0 and by purchasing a 1 month subscription to the Developer level of Wolfram Development Platform, I can report the following differences (which do not affect capability for my use):
$UserBaseDirectory goes to .WolframDesktop rather than .Mathematica. The directory structures otherwise seem to be the same.
This Wolfram Desktop will not use a license file (unlike Mathematica and the Desktop provided with Wolfram|One). Instead, it uses the web and your Wolfram ID. For me, this takes about 5 sec to verify. Potentially, this delay might be a problem for scripts (I haven't tried).
$MaxLicenseSubprocesses = 4 for this Wolfram Desktop. I think this would normally be 8 for Mathematica (for the trial license this is set at 4). Since I have a quad core i7, this probably(?) makes no difference to me.
The big difference: Price. The prices quoted here are in USD, but purchased from Australia. The comparable Mathematica product seems to be Mathematica StandardDesktop/Cloud for industry/personal use. This is \$3060 for the first year, plus \$835/year thereafter for Premier Service Plus to keep the Cloud and receive updates (or \$2780 + \$560/year with no Cloud). On the other hand, a Developer level license for Wolfram Development Platform is priced at $310/year (and presumably includes all updates since there is no mention of a separate service plan). If your Cloud use is minimal (or none at all) then there is nothing further to pay.
By the way, my initial 1 month subscription (for \$31) was refunded when I upgraded the next day to the \$310/year subscription.