No matter what blade you choose for a circular saw the theoretical kerf is going to be around 2mm (CMT go down to 1.9mm) with inevitable breakout on the finished surface and blade flexing it always looks more. Even with a very shallow angle on the chisel you are going nowhere with a 3/4" or 1" oak floorboard unless the chisel is 5 or 6mm thick so when the board is back down on the floor again it will always look crap unless you can shuffle the gaps out of sight. (Yes I do know how to use both the circular saw and the chisel)
When you can cut with a sub 1mm kerf (I just measured a new blade at
0.86mm, a well used but still functional one at 0.55mm), sometimes immediately adjacent to a skirting board in literally minutes, maybe even lifting a single joist span of a single floorboard and then replace the board so the join is almost invisible *every* other solution is a compromise.The last time I had the circular saw boxed up right next to where I wanted to lift a floorboard I used the box purely to rest my cup of tea! While they do have many uses in my experience they are a really, really, crap way of lifting floorboards (as are jigsaws)