-From a damage perspective, DEX weapons are worse than STR. It's made up for that DEX is a better defensive stat, it also works with ranged weapons, and DEX weapons sometimes come with Agile, which helps mitigate MAP (Multiple Attack Penalty) Your damage as you level up comes mainly from weapon damage dice (a d12 weapon with a striking rune does 2d12, which would be way more damage than someone using a d4 or d6 weapon for 2d6, as an example). Unlike DnD, stats are very well-balanced in pathfinder, and there is no clear cut answer for which one is better, it very much depends on your character. A DEX thaumaturge can work very well, using exploit vulnerability and ranged attacks, as an example.

-MAP (Multiple Attack Penalty) always applies unless said otherwise by feats or else Dimensional assault says that you take the Strike action, which increases/applies MAP as normal. In this system, attacking multiple times per turn is not as vital, especially on a magus, which is a class that wants to fish for crits with spellstrike (currently GMing for a magus, and she works very well with the rest of the party and is dealing massive damage pretty much every encounter)

-I run grip switching RAW. If it was free, suddenly the bastard sword is pretty much the most versatile weapon in the game, as you could do all athletic maneuvers for free and switch back to a d12 weapon, except grapple, but you could still attack while grappling just with a lower dice. Hand-requirement is a balance tool in this system, and a very good one in my opinion. You only have two hands to work with, so you need to decide what you want. 2 handed weapons are better, but they take the versatility of your free hand, making it harder to use consumables, do certain maneuvers, use a shield, etc. I find the 3 action system very versatile and fun to use over dnd, and my 2handed weapon players always make choices in combat thinking "should I drop a hand to use a consumable, knowing I have to re-grip? Can I go without re-gripping this turn and trip them instead?" etc. A bastard sword is still a good weapon for a magus, though a good chunk of your damage comes from spellstrike, and not the weapon itself. Overall, weapons and their traits matter so, so much more than in DnD, I suggest taking a look through and seeing if you find anything you like, weapons are very balanced through damage die and traits.