I have a first version 8-element Summicron 35/2 that I find just beautiful for photography. I also like to use the small sized Canon 35mm/2.8 and the 35mm/1.8. The 35mm/2.8 is quite sharp and the 35mm/1.8 shows a lovely glow [or call it flare] when pointed directly at light sources. Cost wise it may be better to go with a CV lens, but signature wise I enjoy my 35mm lenses for what they are and what they deliver. It is quite surprising how the market value of the Canon 35/1.8 has been going up. I have added a Canon 35mm/1.5 to complete the set. The latter lens often has negative review by former users of such a lens, but I found it to be a superb lens when I compared over thirty 35mm-40mm RF lenses. Others concurred here. The Version 1 Summicron has become a collectible lens, and therefore its price is higher than expected. Some claim that it has a special "signature", and others say that this is bogus. Definitely, it is an extremely well made lens that shows how Leica can make lenses.
Canon 35mm/2.8 ............ $150
Canon 35mm/1.8 ............. $350+
Canon 35mm/1.5 ............. $350+
Summicron V1 ................. $750+
Prices can vary depending on the moods of the buyers and sellers when a transaction is being made. The 35mm/2.8 is a best buy.