How how are the two models?
The condition of them would depend on how they were treated. Unlikely you'll find a new TK-272, so buying one off the used market would be anyones guess.
The 2170 is a newer model, and you might be able to get a new one, or a good condition used one. A newer model on the used market is no guarantee that it would be in good condition.
I just. Want to be able to send and rec. and scan the freq that are on the radio. But want a good two radio and nothing old.
Either radio -should- be able to do this, if programmed correctly. New, out of the box, they are not programmed for anything. Buying used can be anyones guess.
Some more info would help:
Where are you located? Rules vary by country, and what might be illegal here in the USA might not be somewhere else. You really should follow the laws in the country you reside in.
Do you have a license for the service you intend to use them in?
Not sure what your level of experience is, some insight into your background would help us steer you in the right direction. The radio will need to be programmed to frequencies you are legally allowed to use. If you don't have any experience programming radios, you should probably rethink this, at least get someone local to help you. To program these radios you would need specific programming software and programming cable. The software isn't impossible to figure out, but if you haven't done it before, it is really easy to make a mistake, or worse, interfere with someone else.