Well, let's break it down. Jace's best ability is probably brainstorming every turn. Chandra's first +1 is probably comparable. She draws you a card. If you can't use that card, it turns into a free shock, which is indistinguishable from a card in a red deck. It's not the same level of card selection, to be sure, but the option for free repeatable damage every turn likely balances that out.
Jace was good at protecting himself with his -1. Chandra's -3 is better, since killing a creature is better than bouncing it. You can't do it as often, but killing a creature tends to be more permanent, so you won't have to do it as often.
Fatesealing ins't bad, but I think ramping by 2 is stronger. Consider that if you have a 2-drop in your hand, Chandra is effectively a 2 mana spell.
Their ultimates both win you the game very quickly, but Chandra's comes online faster.
Like, I don't think she's just equal to Jace. I'm saying she's better than Jace.
I should probably point out that I'm looking at this from a constructed perspective, as that is where the comparisons between her and JTMS fall very, very short.
Brainstorm VS. Exile
In terms of her +1, I'm not sure if you've ever played with Jace in constructed. At it's base, Jace's 0 is brainstorming, and brainstorming is drawing 3 cards (you put the two worst ones back, giving you a virtual 'net gain'). It stops being that once you lock yourself under a brainstorm cycle, but I'll get to that. Chandra's +1 has several limitations.
1. You cannot play lands, as the ability specifies 'cast,' and, well... you can't cast lands.
2. You must play the card that turn.
Now, the obvious response to this is 'but 2 damage!' and this is true; the 2 damage does help mitigate the downsides of the ability, somewhat. It does not, however, completely erase the ability's limitations.
Now let's compare that to JTMS's brainstorm ability, because that's the obvious parallel. Chandra's ability just isn't even close. Remember, we live in a world where fetchlands and shuffle effects exist. Brainstorm would not be half the card it is today without those effects. The ability to shuffle one's library makes brainstorm the ultimate selection tool, so much so that it is restricted in vintage. The ability to literally sculpt (ha) the perfect hand using Jace is a large part of what makes him attractive to your average control deck.
Chandra cannot do that. She provides an equal amount of card raw advantage, with none of virtual card advantage or the selection... sometimes. When you don't hit a land. Or something you don't want to cast. So.... we'll call it 60 percent of the time, to be generous? The other times it's a shock to your opponent, but that doesn't even come close to making up for the biggest issue with her ability: The lack of consistency.
I just don't see how these abilities come close, honestly.
Mini Ritual VS. Fateseal
This mini-ritual does not excite me. People are all like 'wah-wah mitigate her cost,' but what card do you know that's playable in constructed that has a double-red cost? That's what I thought. Maybe, MAYBE you get to double-bolt something, or you're just jamming a 4 drop into burn now because eeeh?
'Mana dump' effects are not typically used in constructed, and fireball effects such as banefire aren't either. I don't think this is enough to make them attractive. But what about next turn? For most decks, the jump from 5-7 mana doesn't really matter. At all. This is frankly an inconsistent ability... which is starting to become a theme here.
There is exactly 1 deck that actually wants this ability: All-In Red, in modern. Maybe dragon/werewolf stompy/Imperial Painter in Legacy want the card, but even then this ability is flavor text.
Fatesealing is always value. You can scry away a bad card for yourself, or a good card for your opponent, or gain the knowledge that they'll be drawing land next turn and use that information to plan your turn. It also is mostly trinket text, as you + to reach his ultimate, but at least it's consistent value.
Bounce VS. 4 damage
Chandra's ability burns a creature for 4. This is not bad. However, there are some veeery important cards that this ability cannot deal with in Legacy (that format that Jace is actually played in), that Jace's can:
Not to mention Marit Lage tokens. I don't think I need to make much more of an argument than this. Burning for 4 is not bad, but it is not a guaranteed tempo advantage against any board state. So, you know... it's inconsistent value.
Ultimate VS. Ultimate
They both win the game more or less the next turn. Willing to call them equal.
Starting Loyalty:
Jace starts with less, but pluses faster. Chandra starts with more, but pluses slower. Neither of them can remove a creature and survive bolt. Both of them can plus and survive bolt. They are equal-ish here enough that I don't have much to talk about.
I guess what I'm trying to say is... JTMS will always be consistent value in constructed. Chandra, much less so.
BUT WHAT ABOUT IN CUUUUUUUUBE?!
There is certainly an environment where this new Chandra is better. To support this, your cube environment must have:
- No shuffle effects.
- Few creatures with toughness over 4
- A highly aggressive creature base
In that environment, I could see this new Chandra being... well, not better, but equal. Ish. Sort of. I've not really convinced myself.
Tl;Dr: Jace is consistent, Chandra is not.