Differences between two closed-loop systems
There are more than just one way to approach the solution:

1) You can find the steady state error by finding the equation of the denominator of the transfer function.

In system 1: 

$$D(s) = a(s)p(s) + b(s)q(s)$$

The order of the system is determined by this order of $D(s)$. Solving for $D(s)$ will give you the poles of the system. If the poles 'solutions of $D(s)$' all are negative. That means if all the values of the solution to $D(s)$ are in the left half plane $&lt;0$. This means the system is stable.

2) The error in time domain is defined as "input - output".
That is:

$$e(t) = y_r(t) - y(t)$$

Now, to compute the steady state error, that is time at infinity 'after a long time'.
The equation will be: $$ e_{ss} = \lim_{t \to \infty}  y_r(t) - y(t) $$
That is simply taking the limit as t goes to infinity.

Now, using the final value theorem to compute the steady state error in the $s$ domain the equation will be:

$$E_{ss} = \lim_{ s \to 0} E$$

That is in your terms

$$E_{ss} = \lim_{s \to 0} s\cdot e_{ss1} \quad(1)$$

$$E_{ss} = \lim_{s \to 0} s\cdot e_{ss2} \quad(2)$$

Therefore; you can note that the result depends on the 'Type of the system and the Input'.
Type of the system: is how many poles at zero do you have?
That is writing:

$$a(s)p(s) + b(s)q(s) = s^n (s+a_0)(s\cdot a_1) \cdot ... \cdot(s\cdot a_{n-1})$$

the value n represents the order of the system.


Type zero means no poles to zero.
Type I means one pole at zero, etc.


Now if the input is a unit step that is $$y_r(s) = \dfrac{1}{s}$$ 
this will cancel out with the $s$ as specified in equations $(1)$ and $(2)$. The equation will be:

$$ e_{ss1} = \lim_{s \to 0} \dfrac{r(s)a(s)}{a(s)p(s)+b(s)q(s)} $$

Now, looking at the type of system: 


If it is of type one or higher, it is clear now that the $e_{ss1}$ goes to
infinity yielding unstable system.
If type zero, it will have a certain value, yet still stable.


These are the techniques, and the answer highly depends on the type of the system or even the characteristic equation that is the equation of the denominator of the transfer function.