Picking spells for a sorcerer at level ups is more newbie-friendly than the memorization process for mages, mages even have to pick beforehand which spells they'll have cast how often. Because of the limited memorization slots mages usually get to cast less different spells than sorcerers during the game. Players don't spend their too few mage memorization spell slots for spells which wouldn't be among the many sorcerer spell picks. Make a list about which spells did your mage cast how often during the game and you'll be surprised.
I've never heard of someone getting stuck because of playing as sorcerer and picking the wrong spells, you can make many bad decisions and still be superior to a mage. To cover all the casting options a sorcerer get mages would need 30 spell slots per level, they only get 5.
If you have a NPC mage among your party members besides your sorcerer you have the advantages of both classes and sorcerers can also cast all mage spells from scrolls.
From the roleplaying point of view sorcerers are far superior to mages with their limited "know one day before exactly what I cast next day" which encourages metagaming.
About picking caster or non-casters as a newbie:
You need to cast spells anyway so it's rather the question if you want to choose a primitive protagonist and hire a caster NPC to put all the thinking and micromanaging effort into him and let him shine over your wimpy character or if you want to concentrate your micromanaging efforts on your character and have him be powerful (and even get benefits as sorcerer NPCs can't get).
If you insist on playing a warrior class I recommend berserker over a paladin kit. Paladins can become fallen if you don't do what the developers consider rightful behavior for your paladin (or simply mess up).
Berserkers level faster and therefore get more hitpoints, proficiencies and high level abilities to pick. Their rage grants the immunities you need in the hard battles.
What starting stats would you recommend for sorcerer or berserker? I think I am leaning towards trying the sorcerer based on your post, simply because there is no sorcerer npc. It seems you need high INT for some of the higher level spells. Also, what alignment for a sorcerer? Alignment will affect your familiar, correct?