Originally Posted by Just Bill
The limit on circuit breaker slots is 40, be it 150 or 200. If you have that many filled, consider a second panel. If you have a smaller panel(<40) replace the panel.
actually, it was 42 but that limitation has been removed but I don't think you are going to see any panels with over 42 spaces anytime soon.
Unless you don't care for having a sub, adding one would be the most cost effective method. If you up-size your service, you are going to have to replace most everything from the utility connection to the panel.
as jairoc stated, unless your load actually calls for an up-size, there is not really any benefit to up-sizing.