It depends what you want!

Etihad business on the 380 is a comfortable seat, as is the 787 (so flights from JFK and IAD in the US) the food is okay, the alcohol selection is okay as in it's decent but nothing wow, and all in all you will have a comfortable flight. Business class on other Etihad planes (all other US airports) won't be particularly comfortable, I've done Etihad's 'old' business class (i.e. Non 787/380) on flights up to eight hours and they have been bearable, I don't think I'd be too happy on a flight from US-UAE on that product. Food and drink and all other aspects is the same as on the A380.

F is a different story. Etihad F on the 380 is a very large room to yourself with a reclining chair on one side and bench that turns into a bed opposite, to the other end of the seat there is a vanity cuboard and a small drinks fridge, you also have a small cupboard to hang your clothes and it is full length although narrow. Bed is firm and the seat doesn't fully recline because of the separate bed but comfort is generally great. The food is hit and miss but it's likely you will have a good meal. Etihad don't use as lavish ingredients as other airlines in F but the presentation is good and usually the taste is too. There is no Caviar, Balik salmon, real Wagyu, etc. as in other airlines F but it's not bad by any means. Similarly for the wines and other drinks there are good ones on offer but perhaps not as high end as you would be served on CX/SQ/NH/JL/AF/LX first class. You won't be disappointed but at the same time you won't be getting any Sassicia or Lynch-Bages.
The 'other' first class products on Etihad (other than the 380) are more or less the same with the exception of the 787 which is again similar to the others (not the 380) with a refreshed interior. It is a good product with good privacy and comfort, food is more or less the same as on the 380 but there is no 'on board chef' which acts more as a service tool than actual better food coming out. You have a chat with the chef about what you want to eat before the meal on the 380. This service isn't there on the other aircrafts. The seat is 'just' a seat it's not a small room like on the 380. It reclines into a bed and you have sliding doors. There's no shower on the other planes, as there is on the 380. Realistically F on the non 380 planes is decent, and not something to avoid; whilst the J product on other aircraft is avoidable. Sure, the A340/777/787 F cabin doesn't have the wow factor of the A380 F, but in practicality it's a good product.
Not to forget the F lounge in AUH is a huge step up from the J lounge.