[Gpa113]

Hi MJ,

Welcome to the forum  
It's a good place to be, and especially for this type of question! 

Personally......
We race Scalextric models.   Slot.it rear tyres, weight added if you want, nasty magnets out, bit of body rock.
Perfectly good race cars, if raced against other Scalextric models. Stacks of cars from many different era's to race, and we get next to no issues with reliability.   Yes, some of the motors do have a fairly big discrepancy,  but it's all part of the game!

I own, but don't necessarily race, many other different brands.
Never had any luck with Fly models.   Only got a handful left now.
Policar I have only some of their bargain models. These are surprisingly good! 
Slot.it are very nice. Well put together and quick. 
NSR.   Yes!!  The proper deal.  Really quick, easy to maintain or upgrade, and super fun to blast around your layout,  whatever size or configuration. 

As the guys have already posted.   The hobbyist brands are pretty compatible.  They are quick out of the box, but if you want to upgrade or tweak these you can.   Scalextric, despite what people say, are great if you want simpler cars to race.
They are no match for the true racing brands, but aren't really meant to be. Race them against themselves, and have a lot of fun.

As usual the big questions are....
Budget, and which are your favoured type of racing classes?  Modern,  Historic,  NASCAR, F1 etc. Or of course the "Wow, that looks cool, love the paint job!" type of purchases we all end up making!