1. The bundled routers of Starhub (HB410 for 3Gbps plan, HB710 for 5Gbps/10Gbps plans) are not as good as the one bundled by M1. Even the EB810v bundled with more expensive 10Gbps plan is not so good due to poor FW, despite the good HW spec (similar to Archer BE800).
So if you want to use the bundled router, or you want to sell them to offset the subscription price, then I tend to think M1 6Gbps plan is better than M1 10Gbps plan in this case.
If you want to use your own router, you can consider M1 10Gbps plan in that case. I tend to believe this is your use case.
2. Purely based on value --> for new users (take note Starhub charges S$2.18 per month for Digital Voice if need that).
Starhub 3Gbps plan > M1 3Gbps plan
Starhub 5Gbps plan = M1 6Gbps plan
Starhub 10Gbps plan < M1 10Gbps plan
3. Starhub new home offer, or Passion Card offer
https://www.starhub.com/personal/forms/hubbing/new-homeowners.html
https://www.starhub.com/personal/promotions/passioncard.html#broadband
3 Gbps plan at S$29.55 per month with free HB410, with free S$50 voucher.
5 Gbps plan at S$38.90 per month, with free HB710, with free S$100 voucher.
10 Gbps plan at S$59.34 per month, with free EB810v, with free S$150 voucher.
(Not worth it).
Starhub has a very good 10Gbps recontract offer at S$30.49 per month with free HB710, but I guess it is not applicable in this case.
4. M1 offer
3Gbps plan at S$32.90 per month, with free Archer BE230 or Asus RT-BE58U
6Gbps plan at S$38.90 per month, with free Archer BE805 or Asus RT-BE92U (for new users)
10Gbps plan at S$34.90 per month, without free router. Top up S$10 per month for Archer BE805, or S$9 per month for Asus RT-BE92U.
10Gbps all-in-one ONR plan at S$38.90 per month, with free Archer BE230 or Asus RT-BE58U
(worst plan from M1, avoid this one)