my vote goes to Manhattan.......u can buy any strategy guide and get all 6 full length tests free.......
I would also recommend MGMAT - two points
1) MGMAT has Excellent data to analyze post test , and believe me this is key to learn from your tests
2) Your performance in Quant at GMAT will probably be closest to your real GMAT.In case of verbal, expect a bit tougher verbal than MGMAT tests.
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