The 40k mentioned above is a bit on the high side to stake on average on a daily basis.
The ROI percentage for staking is the same for all balances. The number mentioned indicates only receiving a reward about every day. I'll not overcomplicate stuff: if a 40k balance gets 1 blockreward per day, you can expect a 4k balance to yield a reward every 10 days, a 400 balance every 100 days, etcetera, etcetera.

It functions like solo mining versus pool mining. If you have the nerves to go without rewards for those periods mentioned, you save yourself the pool fees when staking in your own wallet.
If you're comfortable having your funds under 3rd party control, you may opt for pool mining and enjoy the regular rewards coming in.

If you want to just HODL for future profit, I would certainly keep the wallet staking. Every reward will be a bonus...