A merger agreement that would create a $3.1 billion-asset thrift company with the ninth-largest market share in the Chicago area is getting mixed  reviews. 
MAF Bancorp, Clarendon Hills, Ill., last week said it agreed to pay $277  million to acquire $1.2 billion-asset N.S. Bancorp, Chicago, a franchise   with a low-cost deposit base near MAF's existing market.   
  
"The two companies do not significantly overlap markets," said Allen H.  Koranda, MAF's chairman and chief executive. 
The combined entity would have $275 million in market capital and 20  branches. The deal is expected to close in the first half of 1996. 
  
After a conference call about the merger with management last week, some  analysts still questioned the transaction. 
"I guess I'm a little skeptical," said Christine Pavel, an analyst with  the Chicago Corp. N.S. Bancorp buys many loans from outside the Chicago   area and has a heavy CD deposit base, she said.   
"The bottom line is you don't come in with a lot of good relationships  you can cross-sell," Ms. Pavel said. "I think the revenue enhancement part   of it will be very slow."   
  
However, the deal would push MAF from 16th in market share to ninth,  with 1.82% of Chicago's fragmented market, she said. 
"If, over time, they can even maintain that and shift their deposit  composition toward the core transaction relationship-type deposits, that   will enhance their franchise value," she said.   
Joseph Duwan, an analyst with Keefe, Bruyette & Woods, New York, said  the strategy makes a lot of sense for MAF, but he still expressed   reservations. "What I'm wrestling with now are the financial implications,"   he said.     
The full benefit of the deal will not be seen until mid-1997, after MAF  works through the transition, he said. 
  
After the purchase, MAF will combine the institutions into one thrift  charter, but continue to use the names of the subsidiaries, Mid America   Federal Savings Bank and Northwestern Savings Bank.   
N.S. Bancorp chairman and chief executive Henry Smogolski will retire,  but will be a member of the combined entity's new board, along with another   N.S. executive.   
MAF is financing the deal through $134 million in MAF common stock, $105  million in cash from N.S. Bancorp, and $38 million in debt financing. 
The transaction will be payable in 51% stock and 49% cash, based on  MAF's stock price at the closing. The participants can terminate the   agreement if MAF's average stock price goes above or below certain limits.