Tinyint vs Bit

declare @t table (
    descr varchar(10),
    myBit1 bit,
    myBit2 bit
)
insert into @t values ('test1', 0, 1)
insert into @t values ('test2', 1, 0)
insert into @t values ('test3', 1, 1)
insert into @t values ('test4', 0, 0)

select myBit1, count(myBit1) from @t group by myBit1
select myBit2, count(myBit1) from @t group by myBit2

myBit1
------ -----------
0      2
1      2

myBit2
------ -----------
0      2
1      2