Is chaining two switches different than connecting both switches directly to the router?

Amongst other things (like what haroldmoma mentioned), another to consider is that if you chain the switches together and the first one dies, the second one will also stop working (everyone is offline). If you attach them both to the router, then one failing won't affect the other (only half the office is offline).

When you connect two switches together, you are extending your broadcast domain. The broadcast domain can impose a burden in fairly large networks. When you connect each switch independently to the router, there will be a broadcast domain for each switch, thus controlling the broadcast traffic passing through your network.

If you chain the switches the switch closest to the router will get more traffic than if you had put them parallel (where it will all go through the router) depending on your usage (heavy internet accesses needed vs heavy access to own fileserver) you can weigh one off to the other.

It makes the switch closest to the router a single point of failure (as mentioned by techie007).

Other answers here speak about some of the differences. I will get at your following question,

I know both approaches will work, just wondering if there is a reason to prefer one or the other

So let's say you only use your router for access to inet (no VPN or other routing needs)

If I have Router R_A and switches S_A and S_B. Suppose we connect both switches directly to the router. Then suppose I have 2 hosts on S_A (S_A_h1, S_A_h2) and 2 hosts on S_B (S_B_h1, S_B_h2).

If S_A_h1 wants to talk to S_B_h2 how many hops must be made? 3, one through each switch and the router.

If S_A_h1 wants to reach the internet, how many hops must be made in the LAN? 2, one through the switch and one through the router.

Now suppose we connect only S_A to the router and then connect S_B to S_A.

Now if S_A_h1 wants to talk to S_B_h2 how many hops must be made? 2, one through each of the switches.

If S_B_h2 wants to access the internet how many hops must be made? 3, both switches and the router.

So if you want to reduce network latency you will want to set up your network in such a way that reduces hops. e.g. you would probably want to keep your local media server on the same switch as your TV's and your internet access computers on a switch that connects to the router.