Get the Mega. It's not much more expensive.
You can do an awful lot with the Uno provided that it is a lot of the same job. You are doing different jobs. That changes things immediately and the problems are beyond your control. Different things to be done require different libraries, and that is where the memory goes.
I can see two new libraries coming over the hill, SD and RTC. My stuff is sent to cosm for live view on the internet. In my case the cosm library was the straw that broke the camel's back, and I was obliged to move to Mega 2560.
I think it would be fair to say that, if you want to have a proper system sending data the to internet, a Uno will not suffice. It may be that some smart operators can squeeze it all in by stripping down the libraries. I have no idea about that, but I'm sure you can come to your own conclusions about the merits of such an approach.