I usually prefer open source products over closed source ones, but not with password managers.
When using something like LastPass, and something goes wrong, LastPass will be held accountable by their millions of users. That puts a lot of pressure on them to test things before putting them out in the open, and to fix things as fast as possible. Also, because they exist to make money, they have more of it to put into things such as testing. While I’m sure KeePass is just as secure, if there is a security issue, no one is responsible, it was just a mistake a few hobby developers overlooked. I mean no disrespect to those hobby developers, hobby developers are who run the open source projects(most of the time) I love.
What about Linux? Linux is very important to security, and I use it even though it’s open source. Correct, but Linux is much more widely used and tested that KeePass, it’s also sponsored by many for-profit companies such as Intel.
LastPass also offers a browser extension, and a two factor authentication option for mobile devices. Auto-fill in browsers makes it much easier to use, and makes sure you use LastPass instead of typing in your passwords. That, in turn, leads you to use LastPass to generate passwords, making them more secure. LastPass is also synced across all of my devices, something KeePass doesn’t (natively) offer, and one of the reasons I switched away from mSecure.
While I don’t think that you shouldn’t use a less-known program just because it’s less-known, for something as important as a password manager, it better be pretty good to be less-known. LastPass is well known, and trusted by millions of users, while KeePass is often left out of password manager comparisons, as even the people comparing password managers never heard of it. While open-source is better for security 9/10 times, for my password manager, no open source solution comes close to what LastPass offers.