When it comes to RFB vs. TMO Id say it really just boils down to what the individual player prefers.

I myself prefer TMO over RFB because for me TMO has a better balance between playability, realism and historical accuracy personally I prefer the enemy AI of TMO as well.That is not to say that RFB is a bad mod by any means only that I prefer TMO.

You'd really have to try them both to find the one you like best.Much like test driving a new car.

Comparisons
 

Vaux;
you'll have to decide for yourself. RFB and TMO are both damn good mods. When you decide you'll also want to consider the Run Silent Run Deep campaign mod. While RFB and TMO fixed/upgraded specific gameplay issues, RSRD addresses campaign/historic issues and creates a more authentic scenario (i.e. ships in their proper shipping lanes, famous naval battles taking place at the right time and place etc). Conversely, you can come back from a patrol in RSRD either empty handed or with only one or two sinkings simply because you couldn't find a target. RSRD is definitely not for the "I need action NOW!" crowd but IMHO it makes just one sinking that much more challenging and satisfying.
:salute:

TMO
 

The dds in TMO are really tough. Ducimus has made a great supermod, and I think it is the toughest one out there. FOTRS has great visuals, but is not as difficult (haven't played it for quite some time though.) There are some great mods around too for any of the supermods. Attack mods include Easy Aob and the new 3D TDC, which is good if you want to play with map contacts off. Also, go to the Mobo forum and read about MoBo, a program re manuevering ships. Those mods will keep you busy. RSRDC can be combined with TMO and RFB, and it will insert all of the manor convoys and task forces that were in the Pacific and where there were major (and minor?) battles, the appropriate enemy boats and aircraft will be there.

I am trying to figure out celestial navigation, but I cannot get a handle on it.

Just to update one of my questions....
 

I just got back from my first patrol with my new Salmon class (7th patrol over all), and I did NOT get a Purple Heart. Maybe I just kept banging my shin on some valve in the old S boat? :D