Hi Caitlin @CaitlinH, welcome back to the forum.
For me, the pros far out weighed the cons. Like youn I had used three progressively improved MiniMed paradigm pumps before changing to the Tandem t-Slim x2 January 2019; I had begun using the DexCom G5 sensor July 2018.
I have found that Control IQ [CIQ] is all as advertised and then more - since January my TIR [Time-in-Range] has been over 90%. I had begun using Basal IQ [BIQ] the previous December; note that you can not use both BIQ and CIQ at the same time - once a pump is upgraded to CIQ it can not be down-graded.
A feature I really like about the Tandem pump is its compact size and really sharp screen that I can see with my weak eyes even in bright sub-light. The CIQ algorithm improves on the limited adjustments offered in BIQ and also has the added feature of automatically infusing correction bolus’ at 60%. I suggest that you thoroughly read the User Manual [with its many pages of “warnings”] before using CIQ. For me, the decision to change was very easy.
Some users do not like the orientation of the clip on the pump case; the clip orientation can be changed - also in the User Manual. It took me a while to cet used to how I wear my Tandem; I’ve found that the Tandem fits snugly in an old holster I had gotten with my Paradigm pump.
Another “con” for many is getting used to filling the Tandem cartridge; for me, it took a few/several weeks, but now I do the job as easily as the former MiniMed reservoirs.