Trying to understand the Marriott lingo myself.
eCertificates look like they are the same as the SPG Awards, internal (electronic) paperwork that corresponds to your points booking. Nothing you have to worry about, unless it says you have to supplement the eCertificate with money, in which case it's like the SPG Cash + Points booking. One thing I might like about the Marriott way of doing things is that it appears you can make a points booking, even if you don't currently have the points, as long as you have them 2 weeks in advance of your arrival date.
Upgrade Rewards look like they are the same as SPG Specialty Select points bookings. You have to call in to SPG to see if anything other than a standard room is available for booking with a higher level of points (i.e. upgraded views, Club rooms, junior or full suites, etc). I really like the fact that Marriott appears to just show the options online, making it much quicker to compare what's available for "better" room bookings.