There are a lot of brands used and lots of opinions on which is best. So rather than toss all that out agin I'll just break down the types as you have tossed apples and oranges together in your post.

There are three main control types used, Rheostats, on/off types, and proportional types.

Rheostats are very cheap they are also an off the shelf item but will require wiring. They also need stable room temps to be consistent.

On/off types they vary greatly in pricing generally more than rheostats often less than proportional units. They usually handle the largest amount of power and often are designed for grounded heaters. The probes have lower accuracy than proportional units the vast majority are rated at +/-2º but some are +/-4º ratings. They deliver all or nothing and under some situations this can build a 'swing' where the temps swing from hot to cold and back. Typically they do best with the smallest swing in warm rooms that never get much below 76ºF and with indirect heat or enclosures that have a large thermal mass. (single tubs with UTH fastened to the bottom in regular room temps is about the worst case for them.

Proportional units are generally not priced under $100 (although most entry level ones are around 100$). They are custom designed for the job at hand and have not been adapted from another source so the information is pointed to pets and not plants or HVAC. They feather the temps but doing the same thing as an on off unit but in high speed and click on and off very rapidly many times a second and never allow the heater to hit full power. Effectively the temp you set is basically what it will deliver. The probes have the highest accuracy of any low priced thermometers on the market. It is difficult to buy a thermometer as accurate as most proportional units for the same price. +/- 0.5ºF accuracy. They will deal with almost any conditions the heater has enough power to over come. The range of features is extreme from just temps to just about everything you might want in herp keeping (temp lighting night lighting and humidity with seasonal changes for all of them and email alerts to faults or changes) The more features the higher the price. They basically all have similar specs and so the biggest differences are features and menus.

Pick the type before you decide on brand.