By description, this 914 has inherent understeer if the rear rarely, "came out." Varying degrees of understeer conveys to the driver a sense of stability. This is not bad or good, it is a safe default chassis-suspension tuning choice for all production cars as if the vehicle runs wide in a turn as cornering forces increase, the natural reaction is to increase steering wheel angle... except a chassis-suspension that has inherent understeer does not produce the best track lap times. On a road car it is more often than not, desirable given the many variables that road cars can face (rain, snow, ice, rough roads, and a lot more). How much understeer for a given chassis-suspension can be adjusted-tuned and dialed in to varying degrees.
If the chassis-suspension had inherent oversteer, often means the typical driver will end up off the road in a less than good place. But, a chassis-suspension can be driven to it's adhesion limit with better potential track lap times than a chassis-suspension with inherent understeer at or near it's limit. To achieve this depends a LOT on driver skill and ability.
There is a LOT more than steering input alone to alter the vehicle's direction. Throttle-brakes used to shift weight near the limit of traction can be as or more effective to alter the direction of the vehicle than steering alone. Steering can be used initially used to cause the weigh shift to change vehicle direction with throttle-brakes used to shift weigh increasing the ability to control where the vehicle ends up. Then there is the rear brake lever common to many rally cars today used to essentially lock up rear wheels to force a oversteer condition with weight shift to alter the direction of the chassis-suspension-vehicle.
To do this well, the chassis-suspension needs to have it's CG at the lower back of the driver, near equal weight chassis distribution (where the weight is located has a STRONG effect on how responsive the chassis will be to shifting weight), throttle response, brake balance, steering feel, grip of the tires and much more.
This is one of my fave driver videos, Senna driving a Honda NSX with his foot work in a corner view. Note how Senna uses both throttle-brake-steering to control the NSX's chassis-suspension and his track lines:
https://www.youtube.com/watch?v=8By2AEsGAhU
Jean Ragnotti parking a Renault R5 turbo using power-over steer weight shift, steering and brakes to park this R5 turbo.
https://www.youtube.com/watch?v=BZWeue-NPhY
If the vehicle uses aerodynamics trading off power train output for down force, the chassis-suspension dynamics become more complex.
Ultimate grip for mechanical grip chassis-suspension are mostly tire limited and it is up to the chassis-suspension to keep the tires in their happiest operating conditions.
If the rear of the exxe is sliding out under full power coming out of a corner, this is a chassis set up trait that can be cured with chassis set up and tuning. Both the 914 and exxe can be set up to varying degrees to the meet driver's requirements.
The 914 has a lot more inherent chassis-suspension limitations that restrict what is possible compared to the exxe. Limiting options can be good for those who don't want to or fully understand the complexities, difficulties and fine tune differences of what a really good chassis can do.
The great hidden feature of the exxe is it's chassis-suspension design. It can be set up in many, many ways to meet the driver's needs. The vast majority of production road vehicles built to this day have varying degrees of limitations not found in the exxe. To achieve what is possible in the exxe chassis-suspension is expensive, time consuming requiring a LOT of resources and a really, really GOOD test driver on the best tires & wheels for the expected road types and conditions.
The whole topic of "good handling" is extremely broad, complex and often based on a driver's experience as their point of reference. What is excellent handling for one driver could be beyond awful for another. This is why there is no ideal chassis-suspension set up for all possible vehicles and the conditions of which they operate on.
Compare this to raw power train output with traction in a straight line used to produce zero to spec numbers proven so very effective for marketing of what is considered performance cars.
Bernice
Handling;
The ability to go into a corner hard on the road or an autocross and come out where I want it to.
The Porsche 914 was very predictable. The rear followed the line and rarely went out. The X1/9 can side out the rear end in hard cornering on the throttle. The difference might be the width of the 914. The 914 is wider than an X1/9 and felt more stable in hard turns.