How many State Processes?

Two State Processes

REG: process (CLK, RESET)
begin
    if RESET=`1` then STATE <= START ;
    elsif CLK`event and CLK=`1` then
       STATE <= NEXTSTATE ;
    end if ;
end process REG;

CMB: process (A,B,STATE)
begin
    NEXTSTATE <= STATE ;
    case STATE is
       when START  => if (A or B)=`0` then
                         NEXTSTATE <= MIDDLE ;
                      end if ;
       when MIDDLE => if (A and B)=`1` then
                         NEXTSTATE <= STOP ;
                      end if ;
       when STOP   => if (A xor B)=`1` then
                         NEXTSTATE <= START ;
                      end if ;
       when others => NEXTSTATE <= START ;
    end case ;
end process CMB ;
Y <= ... ;
Z <= ... ;

One State Process

REG: process (CLK, RESET)
begin
    if RESET=`1` then
       STATE <= START ;
    elsif CLK`event and CLK=`1` then
       case STATE is
          when START  => if (A or B)=`0` then
                            STATE <= MIDDLE ;
                         end if ;
          when MIDDLE => if (A and B)=`1` then
                            STATE <= STOP ;
                         end if ;
          when STOP   => if (A xor B)=`1` then
                            STATE <= START ;
                         end if ;
          when others => STATE <= START ;
       end case ;
    end if ;
end process REG ;

Y <= ... ;
Z <= ... ;