I thought I would give my opinions of the new 5. Also a ratio of help you will receive if you are Inspector/Jack. I.E. 20/80 would mean that a character will only help you 20% of the time as the Inspector and this should be used as you are deciding who to use in the picking portion of the extension.
(I25/J75) The character that really changes things is Pizer. If you are Jack you would be silly not to chose him and if you are the inspector you would be asking for trouble if you do. He is the one that has burned me on more than one occasion. I really didn't think his power was that significant until I starting seeing just how much he can change the board.
(I63/J37) Next would be Abberline. I really like him when I am the inspector but he can also be a little frustrating as well. He can really be useful when you are Jack as you can limit or even stop some players movement, but he will almost eliminate your chance of heading towards the exit. Games with Abberline have a significant less chance of ending with an escape. If choosing Pizer as the inspector Abberline is a must to help dampen his authority of the board.
(I51/J49) Third would be Lane. I admit that he is my favorite of the new characters because I just love the barricade. But most of the time the barricade can be overcome, great idea but not as significant as I first thought it would be. No really advantage with either Jack or Inspector.
(I45/J55) Next to last would be Madam. She can really move around the board but it is almost too much and very easy to block. Provides no real advantages to either player.
(I65/J35) Last would be Spring-Heeled Man. He is my least favorite, though at first I thought that I would like him but if I am Jack he is one of the first that I allow to be cleared. I don't know if he will become as obvious as Watson but he is close in my book. What I mean is that in the standard version if you get to the end and there are only two suspects left and Watson is one of them he will be Jack 80% of the time. Now that can be exploited by Jack but most of the time it will turn out to be true.
So in the end yes I do believe that there is some bias toward Jack in the extension but I don't think it is too much so. The bias can really be shaped by who you choose.
Ok I thought I should add my ratio to the other 4 that you could choose from.
(I45/J55) Goodley is great for both players but can really be heightened if combined with Pizer.
(I40/J60) Stealthy is better for Jack and can be really dangerous if combined with Madam. Inspector has to really be on his toes if both are suspects.
(I50/J50) Gull is very balanced, some games he can really not add any flavor at all but others he can be instrumental. Overall though no real advantage for either player.
(I80/J20) Watson is great for the Inspector as he is usually a free cleared suspect thus shortening the game to only 7 suspects. Can be exploited but not done too often.
I hope this helps anyone who is curious and I welcome any other opinions.