Not really noticeable on the road, 205 better for track, especially wet days. A 50 profile will give you more feel, 55 for more pot hole comfort. Much depends on your suspension set up, how you drive & what you really need to pay for a tyre.
Yeh realistically the switch from 195/50 to 205/50 won't really be noticeable. I did once swap from 195/45/16 to 215/40/16. The side walls looked the same but there was at least a noticeable difference in width and grip (using the same tyres as before)
You've got to remember, some brands 195 is the same as 205 of others and vice-verse. Going for the best possible tyre brand and model is the most important thing in my opinion.
Going off all the info I think id go with the 205/50 on the road or track, or put 205 on the back and 195/50 on the front to stop oversteer. my dc2 and last ek9 liked stepping out sometimes and wider tyres on the back cured it