I have no knowledge of these two families but, to answer the original question, yes, the two coats of arms do suggest a close relationship as they are only differenced by the design of the portion "in chief".
Belgraveshed is not quite right in saying "With regard to similar but different coats of arms - these only relate to an individual not a family. If passed on to the next generation then the recipient would have to change some element of it to make it different." . The original Arms would descend to the eldest son undifferenced, whilst other sons would difference their version. This is what may have happened in this case but, if so, which line is the "original" could be hard to discover.
On the other hand, heraldry was not particularly well controlled in England at this time and it is possible that one party has merely adopted similar arms from a family of the same name !
A quick look at Burke's General Armory, unreliable though it is (!), shows a series of Hopson families have similar Arms - 'Ar. on a chev. az. betw. three torteaux' (or variants) and then various charges which might suggest a common origins with your Hobsons. You may need to go back earlier to find the common ground ! Good hunting !
Maec