Amex SPG is the better card to put Marriott and Starwood hotel stays on.
SPG: DH earns 2 SPG points per $1 spent at Starwood and Marriott Rewards hotels, which exchanges 1:3 to Marriott, so the equivalent of 6 Marriott points.
Marriott: DH earns 5 Marriott points per $1 spent at Starwood and Marriott Rewards hotels, which is less than a SPG card's 6 Marriott points.
Note that you can earn points on a SPG card for stays at both Starwood and Marriott properties, but Marriott stays don't count towards SPG status and Starwood stays don't count towards Marriott status. So for now settle on Marriott or Starwood, earn status in one chain and match status from that program to the other.
You can link Marriott and SPG accounts for automatic status match between the two programs:
http://www.marriott.com/marriott-rewards/connect-my-accounts.mi
Marriott Silver Elite translates to SPG Preferred Guest Plus, which is the status you get when you are the primary cardmember of an Amex SPG credit card, so you're not getting anything more there.
Preferred Guest Plus Benefits:
- Earn and redeem at over 1,300 hotels and resorts in nearly 100 countries across 11 hotel brands.
- 2 Starpoints® per eligible US dollar spent.
- Free Night Awards without blackout dates.
- Amazing experiences and access like no other through exclusive partnerships. SPG® is your ticket to the best in music, sports and the arts through our SPG.com/moments auction site.
- Award Flights without blackout dates on over 350 airlines worldwide.
- Upgrades to enhanced rooms at check-in, such as rooms on higher floors or corner rooms.
- 4 p.m. late checkout, where available.
- Other great Starpoints redemption options: transfer Starpoints to miles with over 30 airlines, combine Starpoints with cash for hotel stays, or redeem Starpoints for merchandise awards and more.
I don't know what kind of spend you guys are putting (or expecting to put) on the SPG Biz, but you can achieve Gold status after spending $30,000 on the card in a calendar year, in addition to stays and nights. The Amex Platinums also come with automatic SPG Gold status.
SPG Biz does offer Sheraton club lounge access.
The Marriott cards do offer a free anniversary night stay, but keep in mind it's capped at Category 1-5 hotels.