consider a Master-Child situation, where tblA and tblB is both Master and having the same Child table structure. Some people recommend using the same table as Child for both tblA and tblB as this save resources. Any comments on this? Does it really good or bad? Would it involves higher page read and write? What cost is there actually in having extra tables in SQL Server?
The first thing that could decrease performance is the number of locks on the table, since two table access the your child table (and probably a lot). One disadvantage of having two tables is keeping the data synchronised (and thus more writes). The number of writes depends on how much your data changes. Others disadvantages might be administrating permissions, needing more spaces on your hard disks (depends offcourse on the number of records).
If you are happy with the performance as it is now, I wouldn't change your data model. If the performance is degraded, you could try to select the data in a temporary table (if you have enough ram and the table is small) or change the model to two tables