My reasons:
1: You will find ready customers therein for your Shadow anon service.
2: You will access other services and technologies being built in crypto 2.0.
3: SDC will not loose anything other than the time integrating SuperNet into the wallet which should be easy peasy for SDC Devs.
4: Most importantly you will have access to a wide array of dev talent that can only improve SDC.
5: Lastly SuperNet is one of the few Crypto platforms that has gained value during this bear market.
Please note you won't need to share any source codes or critical SDC resource throughout this process.
SDC is the best Anon island at the moment use this leverage to join the internet of blockchains Crypto 2.0.
Supernet has about 9 months development ahead of Blocknet with 300+ participants on slack http://sprnt.slack.com ...
I am glad we stayed out of Blocknet, but I do agree with your reasons 1 and 4.
Edit.