Too late...I need one by next week...
OK then.
Performance wise, the 12" MacBook is totally fine for your workload most likely. However, you may prefer having the larger screen on the 13" MacBook Pro, esp. if you're going to be using spreadsheets and the like, but it means a 50% increase in weight. Having a 12" MacBook is actually lighter than an iPad with decent keyboard. A 3 lb 13" MacBook Pro is by no means heavy, but the 12" MacBook is so petite that it's very easy to just pick it up and go with it at any time. The 12" is also less awkward to carry and less awkward on a small table. For me that means it's more pleasant to use on a plane, but for you it may also mean it's easy to use on one of those fold up tables in auditorium seats. (I'm not sure though, since I don't need to use my laptop that way.)
Having two ports would be nice though. That way you could charge the Mac while using say a USB drive at the same time. In reality for me though, having the single port hasn't been an issue. Generally when I take it to work I will use it a few hours only, and the battery charge from the morning will be sufficient. However, if I do need to charge it, then I just charge it. For the few minutes I may need to use the USB drive, I can unplug the charging cable and then plug it back in as necessary. There are also USB hubs that allow for charging passthrough if necessary, but they're a bit annoying to carry around.
I had purchased a combo 4K p30 HDMI + USB 3 dongle which also includes charging passthrough but I rarely use it. In fact, the only time I use it is when I need HDMI support, and even then it's at most 1 hour (for a presentation). For USB-A I don't need it because I keep a USB-C to USB-A adapter on my keychain at all times, and use that as necessary. I'm now going to buy a 4K p60 HDMI adapter instead and forget about charging, just so I have a smaller dongle.
So with my 12" MacBook, I bought:
Note that it has on the left front edge a USB-C charging port. However, as mentioned I basically never have to use the charging passthrough, and it's annoying to carry around. Instead, for USB I usually just use what I always have on my keychain:
And I will be buying a simple HDMI 4K p60 dongle for occasional use, something like this:
Note that unlike the MacBook Pro's Thunderbolt 3 port, the USB-C port on the MacBook does not support simultaneous 4K p60 and USB 3. You have to choose, so for a combo dongle it means 4K p60 plus USB 2 or else 4K p30 and USB 3. In my case I will choose to separate them completely, as illustrated above.
tl;dr:
The MacBook is more than fast enough for MS Office. Having 2 USB-C ports would be nice, but most of the time I don't actually need it. What you may prefer is the increased screen real estate of the 13", but for me I much prefer having the smaller and lighter laptop.