It depends, but I would say it is better to keep everything in one table for that sake of simplicity.
100,000 rows a day is not really that much of an enormous amount. (Depending on your server hardware). I have personally seen MSSQL handle up to 100M rows in a single table without any problems. As long as your keep your indexes in order it should be all good. The key is to have heaps of memory so that indexes don't have to be swapped out to disk.
On the other hand, it depends on how you are using the data, if you need to make lots of query's, and its unlikely data will be needed that spans multiple days (so you won't need to join the tables) it will be faster to separate out it out into multiple tables. This is often used in applications such as industrial process control where you might be reading the value on say 50,000 instruments every 10 seconds. In this case speed is extremely important, but simplicity is not.
