As I see it, raising has some advantages and disadvantages. The biggest disadvantage is that SB probably only calls better hands and draws that have a lot of equity. We may get called by a hand like T7x, but even in this best case scenario, villain has >38% equity. Against T9x we are a slight equity dog, at 49.2%, and against any flush draw that doesn’t include an Ace we are in worse shape. We are taking a hand strong enough to call and essentially turning it into a bluff.

We also need to consider how many chips we are investing with a hand that is probably folding to any further betting. If we call the bet and fold to a turn barrel we’ve lost 3k chips. If we raise and get called, check back the turn, and fold to a river bet, we have lost an additional 7.5k chips (not to mention the times villain 3bets the flop). To justify the additional investment we have to believe that raising is accomplishing a fair amount.

One clear advantage is that we give ourselves a chance to win the pot immediately. Every hand at least has overcards to our pair, and folding out that much equity is a big win. I calculated that, if villain is c-betting any less than 90% (of a 62% opening range), we are probably not getting enough folds to profit by raising as a pure bluff. However, raising with at least some equity against villain’s calling range might still be profitable against a much tighter opening/c-betting range. When we are called we can often check-back the turn and see a free river, allowing us to realize our equity. If we make it to showdown our hand will win unimproved against any missed draws (and I expect a lot of draws to call our flop raise), and we will improve to two pair or trips ~21% of the time, beating many of villain’s made hands.

Even if we believe raising is profitable, that doesn’t mean it is more profitable than calling. There’s a lot more to consider, but my brain hurts already, so I’ll stop here for now.

ReinaSafia said
Defending with a hand that doesn’t flop too well post flop especially when you arent getting great odds to call pre is the first issue… Post flop when sb comes in with the lead i think a release is optimal as there arent really any good turn cards for us.

I think BB wants to defend A2o here, as well as a bunch of weaker hands, even though we can be more conservative against a 4x than a smaller open. We will have position for all future betting rounds, and with such deep stacks and inherently wide ranges, position is a huge advantage.

Although I think MDF (minimum defense frequency) is an overvalued concept in a lot of spots, I think it is very relevant in preflop blind defense. If we don’t defend enough hands to prevent villain from profitably opening any two cards then we are giving a lot of free chips away, and incentivizing them to attack our blinds more often.

SB is risking 3500 to win 2500 (500 of his raise is already in the pot as his blind). His raise is auto-profiting if he wins 3500/(3500+2500) = 58.3% of the time. So we need to be defending at least 41.7% of hands. You could build a 42% range without A2o if you prefer defending hands like Q4s,75s,K7o,T8o and similar, but I think we can profitably go much wider than 42% if we trust in our post-flop abilities. Against a SB 3x I’m defending ~80% of hands at >=100 BB and I think at least 65% can be defended against a 4x.

I think BB should almost never be folding a pair on the flop (especially to this size bet), bottom pair included. A reasonable SB opening range flops a pair or better ~38.6% of the time, so any pair should be doing well against most c-betting ranges. Bottom pair with no draw on a monotone or 3 straight board may be good candidates to fold, but otherwise I think it is usually too weak and exploitable to be folding.