What is the best sized 4500 psi tank?

Well i need a litle advice. Im in the market for a air tank to fill my condor and a couple others. I have a small 90 ci 4500 psi tank and it is great but obviously empties quick. I have an AV compressor so it is not a problem to get air. But I mostly shoot at my place 230 miles away upstate and the compressor is heavy to move back and forth as i am not a spring chicken anymore. So do i get the 75 or 98 cf tank? I just dont know if the extra money is worth it to get the 98cf and the extra size and weight. 

The AV tanks are on back order but have free shipping and the Omega is nice too but a little more money and the shipping is expensive.

Any suggestions are welcome and appreciated.
 
Yup What Centercut said! I bought one with 8 years life left delivered (from Seattle to northern Ca.) for $130.00. It is an SCBA tank which are rated by minutes. 60-45-30. Mine is a 60 minute or 80 plus cf. Mine uses a fill station with a CGA347 connection.Watch for what will be needed for what you select. With you having a compressor? maybe the 30 or 45 would be just fine, those of course are cheaper. Good luck sir!
 
88 cf AirHog. You can go with the standard setup but I eventually added the feet and handle later on, much better to carry around.
I opted to go new for safety reason. Even though you have your own compressor you still want to have a used one hydo-test ( tanks should be tested every 5 years) to be sure it is safe to use. these tanks are only supposed to be used for 15 years. Many on eBay only have a few years left. If you buy used, you will still need a regulator. The AirHog regulator allows the air to fill slowly. I used someone else's tank to fill my rifle at EBR and overfill my rifle as it filled extremely fast. 
 
I'd stick with a 45 or 60 minute SCBA tank. The 45 is a little better if you're carrying it around from time to time. The 60 will give you more fills between refills and is nice if you basically leave it in the same spot all the time.
If you're taking it with you a lot, you might consider the 30. But, it sounds like your 90ci would be holding you over for those situations. 
I made my own tank holder out of 2x8 scraps. U shaped and the sides of the "U" are then cut to the same radius as the bottle. Add some sticky back velcro and everything stays put. 
Tom