First, please do research into any specific investment you decide to make and never invest more than you can afford to lose.

Blockchain investing:

The easiest way to invest in a blockchain is by taking a long position on bitcoin which is still risky but historically and still for the time being is the main health indicator in the blockchain economy. You can possibly make more money trading or investing elsewhere but your chances of success will be dependent on your abilities of research, evaluation, and luck.

Service investing:

If you had invested in Coinbase, which supports only the most mainstream blockchains you have a much stronger and stable position than if you invested in an Multi Level Marketing backed company called yo-go which supported one alternate blockchain technology....where did yo-go go? Will I ever see the ROI from that money? I don't think so.... :'(

blockchain v blockchain service:

yes and yes, no and no. there are too many projects and too many blockchains to paint them all with the same colors. It will have to be up to you to decide if an opportunity is worth investing in.

For me personally, I know people that have a high ROI with simply trading in blockchains but I like the idea of being a part of a service. I have a pet project in services I am working on myself which, if successful, would give me a nice ROI but also help the blockchain economy as a whole and make the value of the investments I have in the blockchains increase.....so win win ;)