Once you go back far enough that the Venza has ABS and the truck doesn't, I disagree.
As far as stability issues, yes there are plenty with a dolley. By far the most common comes from the straps not being tight enough or coming loose. I have learned to ALWAYS stop and retighten the straps after taking the first few tight turns after loading up and rolling out. Another issue which is common for me (because i move mostly crapboxes, i suppose) is that if a front tire loses air while towing, the strap of course becomes loose. If a dolley tire blows up it will also immediately go into dangerous sway but that is sometimes true with trailers as well.
I leave towed vehicle steering unlocked on my dolley. If you lock the steering the vehicle pulls MUCH harder on the straps when taking tight turns and is more likely to cause issues. I don't have any stability issues towing this way, at any speed.
RWDs with automatics are a pain to tow on a dolley. I have loaded one backwards on a dolley and locked its steering, but only once as i found it wasnt stable above 45mph and if the road is empty in Texas i prefer something closer to 80. If its an automatic but happens to have a transfer case (4wd) with a neutral position you can use that.
My dolley has an articulated deck (rotates a bit) and if the towed vehicle is too wide it can actually contact the dolley fenders on tight turns. Or used to before i cut the fenders off.
With a loaded dolley you basically cannot back up/reverse at all. It's like pushing a rope. It is sometimes possible to go straight back if your towed vehicle is already perfectly straight behind you.
Another issue with dolleys is that if your hitch ball height isn't right it can put the dolley ramps at too much of an up or down angle and cause them to drag the ground through dips or hit the bottom of your car (bad if you have rocker skirts). Easy to avoid this by just buying the right lift/drop adapter the first time around, though. I have towed my dolley with many many different vehicles, but you wouldn't. Buy one thing and be set forever.
As far as towing trailers, my honest opinion is that yes you do get a decent bump in stability going to a trailer and a lot more utility as it will still tow a wrecked/non-rolling car (as long as you can drag it aboard..) but you don't really get any big upgrade in braking unless you go to a pretty big truck. The last thing i towed was a 9000-lb RV on a ~4-5000lb trailer. I winched the thing on with a 12000lb harbor freight winch and towed it with a ~'15 Ram 3500. That worked well but still felt way more dangerous than any dolley towing i have done! I have towed with a lot of half-ton pickups and didn't find a half ton with a car+16-18ft tandem axle stopped better than a 3000-something lb car towing a loaded dolley. Going from dolley to car-sized trailer you are picking up ~1500 lbs of 'dead weight' so with some smaller trucks you may still be better off with a dolley than a trailer. I also did a lot of towing with a 3800 lb dakota and it never performed well with trailers (although we put as much as 10000lb behind it anyway and just went very slowly). It honestly was never better at any kind of towing than my 3000 lb car other than being able to carry more tongue weight, but a dolley doesn't put much tongue weight on a tow vehicle anyway.
So basically, a dolley can work. If you buy a trailer, get one with brakes. If you buy a new tow vehicle, get one with 4 wheel abs and actually TEST the brakes with full panic stops to verify that they work as they should. Bigger isn't always better and caution and skepticism will buy you more real safety than any amount of hardware.. right up to the point where your tow rig is so heavy that your mistakes are almost guaranteed to kill someone else.