What's the risk of leaving VPP/MCLR floating?
It's not 'floating' in the second circuit, that particular PIC has an internal pull-up. 



You should read the datasheet for the particular processor you are using. It's only 404 pages, a trifle compared to more modern processors. 



Edit: 

If there was no pullup- what would happen: Bad things- it would float around and might reset the micro or not depending on the phase of the moon and how you breath on the PCB (leakages). If you were lucky it would not work at all from the start. 

Some PICs can have the pin re-purposed as an input, in which case that floating around wouldn't have a huge negative effect unless the pin is non-Schmitt trigger, in which case it could cause excessive current draw, more quickly draining a battery, for example. 

It's unlikely to cause any physical damage in any case, but it could cause some problems that appeared to be random and might be hard to troubleshoot (especially if they got blamed on firmware).