As far we can tell there is no difference between an ICO (Initial Coin Offering) vs TGE (Token Generating Event).
The main reason for calling a token offering a TGE is that it does not have coin in the acronym and therefore is potentially less likely to be seen as a security.
Whether or not calling your token offering an Initial Coin Offering or a Token Generating Event will probably not matter as the true test will be what the token itself is and whether or not this is deemed to be a security or a utility token.
The benefit of calling your token offering an ICO vs a TGE is that ICO is more commonly used term in the industry and more widely understood.
On the other hand if you want to try to create as much grey area as possible due to not wanting to be seen as offering a security then calling your token offering a TGE might be advisable.
At blocks ventures we don’t have a preference around whether or not your call your token offering an ICO or a TGE.