When you hear people say they gained anything above 15 lbs on a cycle (after their first), you have to understand that they are either genetically gifted or A LOT of the weight is fat and water, which is far more commonly the case.
I think many of the people on the board are honest about their gains, but I do believe that some (not all) get overzealous when they report their gains.
Remember this atmosphere can be similar to locker room banter where the number of girls you slept with on spring break can suddenly jump from an honest 3 in English class (the period before gym) to 5 or 6 once that locker room door opens.
It took me a long time of reading posts and talking to mods and members (who I learned to trust), before I got a handle on how much LEAN muscle can be expected if you have a full time job or a full time college class load (don't even mention children or a spouse!)
If this is your first cycle, AND you have your nutrition in order, AND you know how to workout well, AND you're committed AND you're disciplined, then yes, 20 lbs of lean muscle is possible if you work your butt off in and out of the gym to keep all your ducks in a row.
If you are not an obsessive person, or you don't have time/dedication to watch your diet, then you will almost definitely gain at least 10 lbs of solid muscle on either of the cycles you listed in your initial post.
If you're gifted genetically--you might gain 15 lbs by only lifting and resting and you might never know exactly why you gained the muscle except that it happened while you were on your cycle.
BTW, my vote is for the lower dose cycle. Even the huge guys at my uh...friend's gym who talk openly about thier steroid use have often suggested 300mg-400mg testosterone enanthate or cypionate with 100- 200mg of deca every week as a beginning cycle. So, taking 250mg of test and 200mg of deca is not unheard of. If you read over some of my other posts, you'll see why I suggest starting with low doses. But do what you feel comfortable doing.
It is true that your first cycle will likely be your highest gaining cycle (if you have your ducks in a row--as mentioned above: diet, lifting, resting).
Best of luck.